fix typo in index_template_substitutions body argument (#3883)

* fix typo in `index_template_substitutions` body argument

* generated files

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Co-authored-by: Laura Trotta <[email protected]>

Author: miguelgrinberg

output/openapi/elasticsearch-openapi.json

@@ -88,7 +88,7 @@ export interface Request extends RequestBase {
     /**
      * A map of index template names to substitute index template definition objects.
      */
-    index_template_subtitutions?: Dictionary<string, IndexTemplate>
+    index_template_substitutions?: Dictionary<string, IndexTemplate>
     mapping_addition?: TypeMapping
     /**
      * Pipelines to test.