remove deprecated train_loop (#10482)

Summary:
### New commit log messages
  fa0ed17f8 remove deprecated train_loop (#10482)

Reviewed By: kandluis

Differential Revision: D32454980

fbshipit-source-id: a35237dde06cc9ddac5373b75992ce88a6771c76

tests/runner/test_runner_lightning_quantization.py

@@ -128,7 +128,7 @@ class TestQuantizationAwareTraining(unittest.TestCase):
                 0,
                 f"step={step}",
             )
-            trainer.train_loop.global_step = step
+            trainer.fit_loop.global_step = step
             qat.on_train_batch_start(
                 trainer, module, batch=None, batch_idx=0, dataloader_idx=0
             )