Revert import change

Author: baskrahmer

tests/tests_pytorch/plugins/precision/test_amp.py

@@ -18,7 +18,7 @@
 from torch import nn
 from torch.optim import Optimizer
 
-from lightning.pytorch.plugins.precision import MixedPrecision
+from lightning.pytorch.plugins import MixedPrecision
 from lightning.pytorch.utilities import GradClipAlgorithmType