Change PUT to POST _search in semantic-text.md example (#134256)

Current example of a semantic highlighter query uses a PUT index API, but it should be a search API.

docs/reference/elasticsearch/mapping-reference/semantic-text.md

@@ -349,7 +349,7 @@ fragments when the field is not of type semantic_text, you can explicitly
 enforce the `semantic` highlighter in the query:
 
 ```console
-PUT test-index
+POST test-index/_search
 {
     "query": {
         "match": {