Drop flaky test.

dulwich/tests/test_refs.py

@@ -356,6 +356,7 @@ class RefsContainerTests(object):
         self.assertNotIn(b"refs/remotes/origin/other", self._refs)
 
     def test_watch(self):
+        self.skipTest("watch sometimes hangs")
         try:
             watcher = self._refs.watch()
         except (NotImplementedError, ImportError):