Unmute FieldSortIT testSortMixedFieldTypes (elastic#138088)

Author: cbuescher

muted-tests.yml

@@ -474,9 +474,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.qa.single_node.PushQueriesIT
   method: testEqualityAndOther {SEMANTIC_TEXT_WITH_KEYWORD}
   issue: https://github.com/elastic/elasticsearch/issues/135333
-- class: org.elasticsearch.search.sort.FieldSortIT
-  method: testSortMixedFieldTypes
-  issue: https://github.com/elastic/elasticsearch/issues/129445
 - class: org.elasticsearch.xpack.esql.expression.function.scalar.score.DecayTests
   method: "testEvaluateInManyThreads {TestCase=<double>, <double>, <double>, <_source> #17}"
   issue: https://github.com/elastic/elasticsearch/issues/135357