Update inner-hits.asciidoc

Typo Closes #19775

Author: clintongormley

docs/reference/search/request/inner-hits.asciidoc

@@ -23,7 +23,7 @@ The structure looks like this:
 }
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-If `_inner_hits` is defined on a query that supports it then each search hit will contain an `inner_hits` json object with the following structure:
+If `inner_hits` is defined on a query that supports it then each search hit will contain an `inner_hits` json object with the following structure:
 
 [source,js]
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