Unmute CcsCommonYamlTestSuiteIT test {p0=search.highlight/50_synthetic_source/text multi unified from vectors} (#127516)

This commit unmutes CcsCommonYamlTestSuiteIT test {p0=search.highlight/50_synthetic_source/text multi unified from vectors}.

The test was observed failing a number of times, by exceeding a timeout. I've rerun the test a number of times and it seems stable now. I'll exercise it in the CI a number of more times, but if it passes successfully then let's unmute it and see if it behaves itself now, since it's possible that the observed failures were caused by a separate or transient issue.

muted-tests.yml

@@ -101,9 +101,6 @@ tests:
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=transform/transforms_reset/Test reset running transform}
   issue: https://github.com/elastic/elasticsearch/issues/117473
-- class: org.elasticsearch.test.rest.yaml.CcsCommonYamlTestSuiteIT
-  method: test {p0=search.highlight/50_synthetic_source/text multi unified from vectors}
-  issue: https://github.com/elastic/elasticsearch/issues/117815
 - class: org.elasticsearch.xpack.ml.integration.RegressionIT
   method: testTwoJobsWithSameRandomizeSeedUseSameTrainingSet
   issue: https://github.com/elastic/elasticsearch/issues/117805