Remove test mute for OldRepositoryAccessIT testOldRepoAccess (#117845)

This has been fixed with #117649 on "main" and the changes causing this
haven't been backported to 8.x. The test was muted due to occasional
timeouts that are unrelated that should have been fixed in the meantime.

Author: cbuescher

muted-tests.yml

@@ -326,9 +326,6 @@ tests:
 - class: org.elasticsearch.xpack.searchablesnapshots.RetrySearchIntegTests
   method: testRetryPointInTime
   issue: https://github.com/elastic/elasticsearch/issues/117116
-- class: org.elasticsearch.oldrepos.OldRepositoryAccessIT
-  method: testOldRepoAccess
-  issue: https://github.com/elastic/elasticsearch/issues/115631
 - class: org.elasticsearch.xpack.inference.InferenceRestIT
   method: test {p0=inference/40_semantic_text_query/Query a field that uses the default ELSER 2 endpoint}
   issue: https://github.com/elastic/elasticsearch/issues/117027