Fix checkpoint callback in test_quantization test

Summary: `checkpoint_callback` now only accepts boolean values: https://github.com/PyTorchLightning/pytorch-lightning/blob/19e67d18c472c3a03dec4dd9bfcef031e9ca8719/pytorch_lightning/trainer/connectors/callback_connector.py#L65-L73

Reviewed By: shuyingsunshine21

Differential Revision: D27682178

fbshipit-source-id: 9e863aad7a23a76dee8ae5df9f5a78e7a94bfe8a

tests/runner/test_runner_lightning_quantization.py

@@ -284,8 +284,7 @@ class TestQuantizationAwareTraining(unittest.TestCase):
         checkpoint = ModelCheckpoint(dirpath=checkpoint_dir, save_last=True)
         trainer = Trainer(
             default_root_dir=os.path.join(root_dir, "quantized"),
-            checkpoint_callback=checkpoint,
-            callbacks=[qat],
+            callbacks=[qat, checkpoint],
             max_epochs=num_epochs,
             logger=False,
         )