Fix mustache search template test (#43120)

This commit fixes a race in the test for the new response format with
search templates. The test indexes a document and then executes a
search with the expectation of 0 results. In some instances, the index
will refresh prior to the search execution and 1 hit will be found
causing the test fail.

Closes #42664

modules/lang-mustache/src/test/resources/rest-api-spec/test/lang_mustache/30_search_template.yml

@@ -137,6 +137,7 @@
         index:  test
         id:     1
         body:   {}
+        refresh: true
 
   - do:
       put_script:
@@ -149,5 +150,5 @@
       search_template:
         body: { "id": "template_1", "params": {} }
 
-  - match: { hits.total.value: 0 }
+  - match: { hits.total.value: 1 }
   - match: { hits.total.relation: eq }