Unmute ComparisonTests (#114248)

Closes #111721

The test got muted time ago. I'm unmuting it because: - I couldn't
reproduce it. The test uses an accuracy delta for assertions, so I
executed it _in a loop_ in case there was some edge case with it, but no
luck - The classes were heavily changed

Author: ivancea

muted-tests.yml

@@ -71,9 +71,6 @@ tests:
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=rollup/security_tests/Index-based access}
   issue: https://github.com/elastic/elasticsearch/issues/111631
-- class: org.elasticsearch.tdigest.ComparisonTests
-  method: testSparseGaussianDistribution
-  issue: https://github.com/elastic/elasticsearch/issues/111721
 - class: org.elasticsearch.upgrades.FullClusterRestartIT
   method: testSnapshotRestore {cluster=OLD}
   issue: https://github.com/elastic/elasticsearch/issues/111777