Make indices.get_mapping::query.index not required (#411)

Signed-off-by: Theo Truong <[email protected]>

Author: nhtruong

Diff for: spec/namespaces/indices.yaml

@@ -3837,7 +3837,6 @@ components:
         Comma-separated list of data streams, indices, and aliases used to limit the request.
         Supports wildcards (`*`).
         To target all data streams and indices, omit this parameter or use `*` or `_all`.
-      required: true
       schema:
         $ref: '../schemas/_common.yaml#/components/schemas/Indices'
       style: simple