Update strategy import statements (#11238)

Co-authored-by: Adrian Wälchli <[email protected]>

Author: kaushikb11

docs/source/common/checkpointing.rst

@@ -348,7 +348,8 @@ Custom Checkpoint IO Plugin
 
     from pytorch_lightning import Trainer
     from pytorch_lightning.callbacks import ModelCheckpoint
-    from pytorch_lightning.plugins import CheckpointIO, SingleDeviceStrategy
+    from pytorch_lightning.plugins import CheckpointIO
+    from pytorch_lightning.strategies import SingleDeviceStrategy
 
 
     class CustomCheckpointIO(CheckpointIO):

pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -34,7 +34,6 @@
     NativeMixedPrecisionPlugin,
     PrecisionPlugin,
     ShardedNativeMixedPrecisionPlugin,
-    Strategy,
     TPUBf16PrecisionPlugin,
     TPUPrecisionPlugin,
     TrainingTypePluginsRegistry,
@@ -60,6 +59,7 @@
     IPUStrategy,
     SingleDeviceStrategy,
     SingleTPUStrategy,
+    Strategy,
     TPUSpawnStrategy,
 )
 from pytorch_lightning.utilities import (