help: Offer links to "Search filters" for logged in users.

- Replaces instructions for opening the search filters reference
  with `{relative|gear|search-filters}`.

help/search-for-messages.md

@@ -154,10 +154,7 @@ A summary of the search filters above is available in the Zulip app.
 
 {start_tabs}
 
-1. Click the **keyboard** (<i class="fa fa-keyboard-o"></i>) icon at the bottom
-   of the app, just below the right sidebar.
-
-1. Switch to the **Search filters** tab.
+{relative|gear|search-filters}
 
 {end_tabs}
 

zerver/lib/markdown/help_relative_links.py

@@ -28,6 +28,7 @@ gear_info = {
     "invite": ["Invite users", "/#invite"],
     "keyboard-shortcuts": ["Keyboard shortcuts (?)", "/#keyboard-shortcuts"],
     "message-formatting": ["Message formatting", "/#message-formatting"],
+    "search-filters": ["Search filters", "/#search-operators"],
     "about-zulip": ["About Zulip", "/#about-zulip"],
 }