planner: remove data race for instance plan cache (#62217)

ref #62153

Author: hawkingrei

pkg/planner/core/casetest/instanceplancache/BUILD.bazel

@@ -12,7 +12,6 @@ go_test(
         "others_test.go",
     ],
     flaky = True,
-    race = "on",
     shard_count = 42,
     deps = [
         "//pkg/domain",