[8.16][TEST] Add missing required feature to yaml tests (#116010)

* Update muted-tests.yml

* Update 20_synthetic_source.yml

Author: kkrik-es

muted-tests.yml

@@ -346,15 +346,6 @@ tests:
 - class: org.elasticsearch.reservedstate.service.FileSettingsServiceTests
   method: testProcessFileChanges
   issue: https://github.com/elastic/elasticsearch/issues/115280
-- class: org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT
-  method: test {p0=indices.create/20_synthetic_source/object with unmapped fields}
-  issue: https://github.com/elastic/elasticsearch/issues/115910
-- class: org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT
-  method: test {p0=indices.create/20_synthetic_source/empty object with unmapped fields}
-  issue: https://github.com/elastic/elasticsearch/issues/115911
-- class: org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT
-  method: test {p0=indices.create/20_synthetic_source/nested object with unmapped fields}
-  issue: https://github.com/elastic/elasticsearch/issues/115912
 
 # Examples:
 #

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/indices.create/20_synthetic_source.yml

@@ -1,6 +1,6 @@
 object with unmapped fields:
   - requires:
-      cluster_features: ["mapper.track_ignored_source"]
+      cluster_features: ["mapper.ignored_source.dont_expand_dots"]
       reason: requires tracking ignored source
 
   - do:
@@ -100,7 +100,7 @@ unmapped arrays:
 ---
 nested object with unmapped fields:
   - requires:
-      cluster_features: ["mapper.track_ignored_source"]
+      cluster_features: ["mapper.ignored_source.dont_expand_dots"]
       reason: requires tracking ignored source
 
   - do:
@@ -152,7 +152,7 @@ nested object with unmapped fields:
 ---
 empty object with unmapped fields:
   - requires:
-      cluster_features: ["mapper.track_ignored_source"]
+      cluster_features: ["mapper.ignored_source.dont_expand_dots"]
       reason: requires tracking ignored source
 
   - do: