Fix pharse suggest collate example to use correct script context/syntax

Closes #15675

docs/reference/search/suggesters/phrase-suggest.asciidoc

@@ -192,9 +192,11 @@ curl -XPOST 'localhost:9200/_search' -d {
          } ],
          "collate": {
            "query": { <1>
+             "inline" : {
                "match": {
                    "{{field_name}}" : "{{suggestion}}" <2>
                }
+             }
            },
            "params": {"field_name" : "title"}, <3>
            "prune": true <4>

modules/lang-mustache/src/test/java/org/elasticsearch/messy/tests/SuggestSearchTests.java

@@ -1166,11 +1166,12 @@ public class SuggestSearchTests extends ESIntegTestCase {
         String filterString = XContentFactory.jsonBuilder()
                     .startObject()
                         .startObject("match_phrase")
-                            .field("title", "{{suggestion}}")
+                            .field("{{field}}", "{{suggestion}}")
                         .endObject()
                     .endObject()
                 .string();
         PhraseSuggestionBuilder filteredQuerySuggest = suggest.collateQuery(filterString);
+        filteredQuerySuggest.collateParams(Collections.singletonMap("field", "title"));
         searchSuggest = searchSuggest("united states house of representatives elections in washington 2006", filteredQuerySuggest);
         assertSuggestionSize(searchSuggest, 0, 2, "title");