Stabilize Basler timeout mapping test

Update the hardware-trigger timeout test to raise `bb.genicam.TimeoutException` directly instead of a fake timeout class, and assert that this real pylon exception is preserved as the `__cause__` of the mapped `TimeoutError`. This keeps the test aligned with actual backend behavior.

Author: C-Achard

tests/cameras/backends/test_basler_backend.py

@@ -487,8 +487,10 @@ class FakePylonTimeout(Exception):
     backend = bb.BaslerCameraBackend(settings)
     backend.open()
 
+    pylon_to = bb.genicam.TimeoutException
+
     def raise_timeout(*_args, **_kwargs):
-        raise FakePylonTimeout("Grab timed out")
+        raise pylon_to("Simulated timeout")
 
     monkeypatch.setattr(backend._camera, "RetrieveResult", raise_timeout)
 
@@ -499,7 +501,7 @@ def raise_timeout(*_args, **_kwargs):
         ) as exc_info:
             backend.read()
 
-        assert isinstance(exc_info.value.__cause__, FakePylonTimeout)
+        assert isinstance(exc_info.value.__cause__, bb.genicam.TimeoutException)
 
     finally:
         backend.close()