Remove fixed test from muted-tests.yml (#124088)

The issue underlying this test mute has been closed as a duplicate, the
issue seems fixed in #117415 
but the test wasn't activated again.

Author: cbuescher

muted-tests.yml

@@ -122,8 +122,6 @@ tests:
 - class: org.elasticsearch.xpack.ccr.rest.ShardChangesRestIT
   method: testShardChangesNoOperation
   issue: https://github.com/elastic/elasticsearch/issues/118800
-- class: org.elasticsearch.xpack.security.authc.ldap.ActiveDirectoryRunAsIT
-  issue: https://github.com/elastic/elasticsearch/issues/115727
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=transform/transforms_start_stop/Test start/stop/start transform}
   issue: https://github.com/elastic/elasticsearch/issues/119508