[flakey] Skip ray_syncer_test for ubsan.

[fishbone]

Why are these changes needed?

From the message:

[       OK ] SyncerTest.TestMToN (13132 ms)
[----------] 5 tests from SyncerTest (43175 ms total)

[----------] Global test environment tear-down
[==========] 8 tests from 2 test suites ran. (43176 ms total)
[  PASSED  ] 8 tests.
external/com_github_grpc_grpc/src/core/lib/iomgr/ev_posix.cc:314:19: runtime error: member access within null pointer of type 'const struct grpc_event_engine_vtable'

This can only be reproduced by running with Bazel test so far. With gdb, it won't be reproduced. It seems like some issue with the grpc maybe the reactor API.
Given that the ASAN test, which is supposed to catch the issue, runs well, and a considerable time has been spent investigating this one but no progress, skip this test for now.

Related issue number

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(