tests: add can't add segment to log allow list

The error may happen as a natural consequence of a race condition
between two segments uploads. It shouldn't make the tests to fail

Signed-off-by: Michal Maslanka <michal@redpanda.com>

tests/rptest/tests/cloud_storage_timing_stress_test.py

@@ -515,6 +515,7 @@ def test_cloud_storage(self, cleanup_policy):
             r"Error in hydraton loop: .*Connection reset by peer",
             r"failed to hydrate chunk.*Connection reset by peer",
             r"failed to hydrate chunk.*NotFound",
+            r"cluster.*Can't add segment",
         ])
     @parametrize(cleanup_policy="delete")
     @parametrize(cleanup_policy="compact,delete")