Remove fixed test from muted-tests.yml

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

Author: cbuescher

muted-tests.yml

@@ -128,8 +128,6 @@ tests:
 - class: org.elasticsearch.cluster.service.MasterServiceTests
   method: testThreadContext
   issue: https://github.com/elastic/elasticsearch/issues/118914
-- class: org.elasticsearch.xpack.security.authc.ldap.ActiveDirectoryRunAsIT
-  issue: https://github.com/elastic/elasticsearch/issues/115727
 - class: org.elasticsearch.index.mapper.AbstractShapeGeometryFieldMapperTests
   method: testCartesianBoundsBlockLoader
   issue: https://github.com/elastic/elasticsearch/issues/119201