Move painless context api spec to test local (#43122)

The painless context api is internal and currently meant only for use in
generating docs. This commit moves the spec file for the api so that it
is only used by the test for this api, and not externally by any clients
building from the public rest spec.

client/rest-high-level/src/test/java/org/elasticsearch/client/RestHighLevelClientTests.java

@@ -710,8 +710,8 @@ public class RestHighLevelClientTests extends ESTestCase {
             "indices.exists_type",
             "indices.get_upgrade",
             "indices.put_alias",
-            "render_search_template",
-            "scripts_painless_execute"
+            "scripts_painless_execute",
+            "render_search_template"
         };
         //These API are not required for high-level client feature completeness
         String[] notRequiredApi = new String[] {
@@ -731,7 +731,6 @@ public class RestHighLevelClientTests extends ESTestCase {
             "nodes.hot_threads",
             "nodes.usage",
             "nodes.reload_secure_settings",
-            "scripts_painless_context",
             "search_shards",
         };
         List<String> booleanReturnMethods = Arrays.asList(