Dsiable flaky test in oss test_zch_hash_disable_fallback (#3425)

Summary:

as titled.

Differential Revision: D83786896

Author: Yixin Bao

torchrec/modules/tests/test_hash_mc_modules.py

@@ -694,7 +694,8 @@ def test_dynamically_switch_inference_training_mode(self) -> None:
         torch.cuda.device_count() < 1,
         "Not enough GPUs, this test requires at least two GPUs",
     )
-    def test_zch_hash_disable_fallback(self) -> None:
+    def test_zch_hash_disable_fallback_disabled_in_oss_compatibility(self) -> None:
+        # TODO: fix this flaky test in OSS.
         m = HashZchManagedCollisionModule(
             zch_size=30,
             device=torch.device("cuda"),