webhook_md_macros: Stop using transition words.

Transition words make it harder to reuse macros in different
contexts and can lead to unintended errors. Thanks to Rishi
Gupta for suggesting this!

templates/zerver/help/include/create-a-bot-indented.md

@@ -1,4 +1,4 @@
-    Next, on your {{ settings_html|safe }},
+    On your {{ settings_html|safe }},
     [create a bot](/help/add-a-bot-or-integration) for
     {{ integration_display_name }}. Make sure that you select
     **Incoming webhook** as the **Bot type**:

templates/zerver/help/include/create-a-bot.md

@@ -1,4 +1,4 @@
-Next, on your {{ settings_html|safe }},
+On your {{ settings_html|safe }},
 [create a bot](/help/add-a-bot-or-integration) for
 {{ integration_display_name }}. Make sure that you select
 **Incoming webhook** as the **Bot type**:

templates/zerver/help/include/create-bot-construct-url-indented.md

@@ -1,6 +1,6 @@
     {!create-a-bot-indented.md!}
 
-    Now, construct the URL for the {{ integration_display_name }}
+    Construct the URL for the {{ integration_display_name }}
     bot using the bot's API key and the desired stream name:
 
     {!webhook-url.md!}

templates/zerver/help/include/create-stream.md

@@ -1,4 +1,4 @@
-First, create the stream you'd like to use for
+Create the stream you'd like to use for
 {{ integration_display_name }} notifications, and subscribe all
 interested parties to this stream. We recommend the
 name `{{ recommended_stream_name }}`. You still need to create