fix mobilnet norm layer test (#5643)

* xfail mobilnet norm layer test

* fix test

Author: pmeier

test/test_models.py

@@ -406,7 +406,7 @@ def test_mobilenet_norm_layer(model_fn):
     assert any(isinstance(x, nn.BatchNorm2d) for x in model.modules())
 
     def get_gn(num_channels):
-        return nn.GroupNorm(32, num_channels)
+        return nn.GroupNorm(1, num_channels)
 
     model = model_fn(norm_layer=get_gn)
     assert not (any(isinstance(x, nn.BatchNorm2d) for x in model.modules()))