onboarding: Use 'remove_single_newlines' once, while sending message.

Instead of applying 'remove_single_newlines()' to individual
contents when declared, we use it once while prepping up
message in 'internal_prep_stream_message_by_name'.

Just for the code to be less finnicky.

zerver/lib/onboarding.py

@@ -276,18 +276,16 @@ def send_initial_realm_messages(realm: Realm) -> None:
         #
         # remove_single_newlines needs to be called on any multiline
         # strings for them to render properly.
-        content1_of_moving_messages_topic_name = remove_single_newlines(
-            (
-                _("""
+        content1_of_moving_messages_topic_name = (
+            _("""
 If anything is out of place, it’s easy to [move messages]({move_content_another_topic_help_url}),
 [rename]({rename_topic_help_url}) and [split]({move_content_another_topic_help_url}) topics,
 or even move a topic [to a different channel]({move_content_another_channel_help_url}).
 """)
-            ).format(
-                move_content_another_topic_help_url="/help/move-content-to-another-topic",
-                rename_topic_help_url="/help/rename-a-topic",
-                move_content_another_channel_help_url="/help/move-content-to-another-channel",
-            )
+        ).format(
+            move_content_another_topic_help_url="/help/move-content-to-another-topic",
+            rename_topic_help_url="/help/rename-a-topic",
+            move_content_another_channel_help_url="/help/move-content-to-another-channel",
         )
 
         content2_of_moving_messages_topic_name = _("""
@@ -298,42 +296,34 @@ or even move a topic [to a different channel]({move_content_another_channel_help
 Zulip is organized to help you communicate more efficiently.
 """)
 
-        content2_of_welcome_to_zulip_topic_name = remove_single_newlines(
-            (
-                _("""
+        content2_of_welcome_to_zulip_topic_name = (
+            _("""
 In Zulip, **channels** determine who gets a message.
 
 Each conversation in a channel is labeled with a **topic**.  This message is in
 the #**{zulip_discussion_channel_name}** channel, in the "{topic_name}" topic, as you can
 see in the left sidebar and above.
 """)
-            ).format(
-                zulip_discussion_channel_name=str(Realm.ZULIP_DISCUSSION_CHANNEL_NAME),
-                topic_name=_("welcome to Zulip!"),
-            )
+        ).format(
+            zulip_discussion_channel_name=str(Realm.ZULIP_DISCUSSION_CHANNEL_NAME),
+            topic_name=_("welcome to Zulip!"),
         )
 
-        content3_of_welcome_to_zulip_topic_name = remove_single_newlines(
-            _("""
+        content3_of_welcome_to_zulip_topic_name = _("""
 You can read Zulip one conversation at a time, seeing each message in context,
 no matter how many other conversations are going on.
 """)
-        )
 
-        content4_of_welcome_to_zulip_topic_name = remove_single_newlines(
-            _("""
+        content4_of_welcome_to_zulip_topic_name = _("""
 :point_right: When you're ready, check out your [Inbox](/#inbox) for other
 conversations with unread messages. You can come back to this conversation
 if you need to from your **Starred** messages.
 """)
-        )
 
-        content1_of_start_conversation_topic_name = remove_single_newlines(
-            _("""
+        content1_of_start_conversation_topic_name = _("""
 To kick off a new conversation, click **Start new conversation** below.
 The new conversation thread won’t interrupt ongoing discussions.
 """)
-        )
 
         content2_of_start_conversation_topic_name = _("""
 For a good topic name, think about finishing the sentence: “Hey, can we chat about…?”
@@ -376,9 +366,8 @@ This **greetings** topic is a great place to say "hi" :wave: to your teammates.
 :point_right:  Click on any message to start a reply in the same topic.
 """)
 
-        content_of_zulip_update_announcements_topic_name = remove_single_newlines(
-            (
-                _("""
+        content_of_zulip_update_announcements_topic_name = (
+            _("""
 Welcome! To help you learn about new features and configuration options,
 this topic will receive messages about important changes in Zulip.
 
@@ -387,10 +376,9 @@ You can read these update messages whenever it's convenient, or
 If your organization does not want to receive these announcements,
 they can be disabled. [Learn more]({zulip_update_announcements_help_url}).
             """)
-            ).format(
-                zulip_update_announcements_help_url="/help/configure-automated-notices#zulip-update-announcements",
-                mute_topic_help_url="/help/mute-a-topic",
-            )
+        ).format(
+            zulip_update_announcements_help_url="/help/configure-automated-notices#zulip-update-announcements",
+            mute_topic_help_url="/help/mute-a-topic",
         )
 
     welcome_messages: List[Dict[str, str]] = []
@@ -482,7 +470,7 @@ they can be disabled. [Learn more]({zulip_update_announcements_help_url}).
             welcome_bot,
             message["channel_name"],
             message["topic_name"],
-            message["content"],
+            remove_single_newlines(message["content"]),
         )
         for message in welcome_messages
     ]