Update docs/usage/mappings.asciidoc

Co-authored-by: Marci W <333176+marciw@users.noreply.github.com>

Author: flobernd

docs/usage/mappings.asciidoc

@@ -4,7 +4,7 @@
 This page demonstrates how to configure custom mappings on an index.
 
 [discrete]
-=== Configure Mappings during Index Creation
+=== Configure mappings during index creation
 
 [source,csharp]
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