ksearch: remove Zendesk/Algolia/Bing (#272)

These three backend types are no longer used/supported,
so this PR removes them and their associated code.

J=WAT-4331
TEST=auto

Updated and ran tests

---------

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

docs/search-core.source.md

@@ -19,15 +19,16 @@ export declare enum Source
 =======
 |  Member | Value | Description |
 |  --- | --- | --- |
-|  Algolia | <code>&quot;ALGOLIA&quot;</code> | The result is from Algolia. |
-|  Bing | <code>&quot;BING_CSE&quot;</code> | The result is from Bing Search Engine. |
 |  Custom | <code>&quot;CUSTOM_SEARCHER&quot;</code> | The result was from a custom source. |
 |  DocumentVertical | <code>&quot;DOCUMENT_VERTICAL&quot;</code> | The result is from a document vertical. |
 |  FunctionVertical | <code>&quot;FUNCTION_VERTICAL&quot;</code> | The result is from a function vertical. |
 |  Google | <code>&quot;GOOGLE_CSE&quot;</code> | The result is from Google Custom Search Engine. |
 |  KnowledgeManager | <code>&quot;KNOWLEDGE_MANAGER&quot;</code> | The result is from a Knowledge Graph. |
+<<<<<<< HEAD
 |  Zendesk | <code>&quot;ZENDESK&quot;</code> | The result is from Zendesk. |
 >>>>>>> 97e068e (search-core: add support for FunctionVertical (#271))
+=======
+>>>>>>> 4f71562 (ksearch: remove Zendesk/Algolia/Bing (#272))
 
 Member