help: Convert emoji images to unicode emoji.

We had inconsistencies in the documentation where we were using emojis
directly in help documentations and sometimes we were using an img tag
for it. This commit aims to standardise it to just using emojis
directly.
See https://chat.zulip.org/#narrow/stream/19-documentation/topic/help.20center.20-.20emojis.20in.20markdown.20files/near/1954272
on more details on the decision.

help/configure-emoticon-translations.md

@@ -1,19 +1,7 @@
 # Configure emoticon translations
 
 You can configure whether emoticons like `:)` or `:(` will be automatically
-translated into emoji equivalents like
-<img
-    src="/static/generated/emoji/images-google-64/1f642.png"
-    alt="smile"
-    class="emoji-small"
-/>
-or
-<img
-    src="/static/generated/emoji/images-google-64/1f641.png"
-    alt="slight_frown"
-    class="emoji-small"
-/>
-by Zulip.
+translated into emoji equivalents like 🙂 or 🙁 by Zulip.
 
 ## Configure emoticon translations
 

help/emoji-and-emoticons.md

@@ -47,13 +47,7 @@
 ### Use an emoticon
 
 You can configure Zulip to convert emoticons into emoji, so that, e.g., `:)`
-will be displayed as
-<img
-    src="/static/generated/emoji/images-google-64/1f642.png"
-    alt="smile"
-    class="emoji-small"
-/>
-.
+will be displayed as 🙂 .
 
 {start_tabs}
 

help/emoji-reactions.md

@@ -32,9 +32,7 @@ message.
 
 !!! keyboard_tip ""
 
-    You can react to the selected message with <img alt=":thumbs_up:"
-    class="emoji" src="/static/generated/emoji/images/emoji/unicode/1f44d.png"
-    title="thumbs up"/> by using the <kbd>+</kbd> shortcut.
+    You can react to the selected message with 👍 by using the <kbd>+</kbd> shortcut.
 
 {tab|mobile}
 

help/keyboard-shortcuts.md

@@ -185,9 +185,7 @@ in the Zulip app to add more to your repertoire as needed.
 
 * **Star message**: <kbd>Ctrl</kbd> + <kbd>S</kbd>
 
-* **React with <img alt=":thumbs_up:" class="emoji"
-  src="/static/generated/emoji/images/emoji/unicode/1f44d.png"
-  title="thumbs up"/>**: <kbd>+</kbd>
+* **React with 👍**: <kbd>+</kbd>
 
 * **Toggle first emoji reaction**: <kbd>=</kbd>
 

help/search-for-messages.md

@@ -41,9 +41,7 @@ Some details to keep in mind:
 - Zulip search ignores very common words like `a`, `the`, and about 100 others.
 - [Emoji](/help/emoji-and-emoticons) in messages (but not [emoji
   reactions](/help/emoji-reactions)) are included in searches, so if you search
-  for `octopus`, your results will include messages with the `:octopus:` emoji (
-  <img src="/static/generated/emoji/images-google-64/1f419.png" alt="octopus"
-  class="emoji-small"/>).
+  for `octopus`, your results will include messages with the `:octopus:` emoji (🐙).
 
 ## Search filters