DOCSP-54057 Change refernce to S10 search tier to S20 (#14655)

Author: kanchana-mongodb

content/atlas/source/atlas-search/about/deployment-options.txt

@@ -67,7 +67,7 @@ and search tiers for performing vector search.
    * - Production
      - Dedicated {+cluster+} with separate Search Nodes, sharded or
        unsharded 
-     - ``M10`` or higher {+cluster+} tier and ``S10`` or higher search
+     - ``M10`` or higher {+cluster+} tier and ``S20`` or higher search
        tier 
      - |aws| and |azure| in some :ref:`regions <fts-cloud-provider-regions>` 
        or |gcp| in all regions