docs: Rename "operators" to "filters".

Changes all the uses of the word "operators" to "filters" in
contributor docs, help center, and landing page to align with
the updated help center documentation.

docs/subsystems/full-text-search.md

@@ -7,8 +7,8 @@ supports English text, but there is an experimental
 full-text search for all languages.
 
 The user interface and feature set for Zulip's full-text search is
-documented in the "Search operators" documentation section in the Zulip
-app's gear menu.
+documented in the in-app "Search filters" reference which can be
+accessed from the Zulip app's gear menu.
 
 ## The default full-text search implementation
 

docs/testing/manual-testing.md

@@ -531,7 +531,7 @@ Make sure that these options launch appropriate help screens:
 
 - Proofread and try a couple random options:
   - Message formatting
-  - Search operators
+  - Search filters
 - Make sure help launches in a separate browser tab:
   - Desktop and mobile apps
   - Integrations

templates/corporate/development-community.md

@@ -219,7 +219,7 @@ you.
 ## Searching for past conversations
 
 To look for previous threads about something, we recommend using the
-following [search operators](/help/search-for-messages):
+following [search filters](/help/search-for-messages#search-filters):
 `streams:public <your keyword(s)>`.
 
 This will search the full history of all public streams for `<your

templates/corporate/features.html

@@ -159,7 +159,7 @@
             <p>
                 Search is both snappy and smart, helping you look for
                 text, people, and threads of conversation, with advanced
-                search operators for fine-grained control.
+                search filters for fine-grained control.
             </p>
         </a>
         <a class="feature-block" href="/help/stream-permissions" target="_blank" rel="noopener noreferrer">

templates/zerver/help/resolve-a-topic.md

@@ -15,7 +15,7 @@ Marking a topic as resolved:
   you resolved the topic. This message will be marked as unread
   only for users who had participated in the topic.
 * Changes whether the topic appears when using the `is:resolved` and
-  `-is:resolved` [search operators](/help/search-for-messages).
+  `-is:resolved` [search filters](/help/search-for-messages#search-filters).
 
 Marking a topic as unresolved removes the ✔ and also triggers an
 automated notice from the notification bot.