[fbgemm_gpu] upgrade ROCm to 6.4.2

Author: q10

.github/scripts/generate_ci_matrix.py

@@ -311,9 +311,9 @@ def cuda_versions(self) -> List[str]:
 
     def rocm_versions(self) -> List[str]:
         if GitRepo.ref() == REFS_MAIN and GitRepo.event_name() == EVENT_NAME_PUSH:
-            return ["6.4"]
+            return ["6.4.2"]
         else:
-            return ["6.3", "6.4"]
+            return ["6.3", "6.4.2"]
 
     def host_machines(self) -> List[Dict[str, str]]:
         # For the list of available instance types: