remove message (#8163)

Author: awaelchli

pytorch_lightning/metrics/__init__.py

@@ -38,9 +38,3 @@
     R2Score,
     SSIM,
 )
-from pytorch_lightning.utilities import rank_zero_deprecation
-
-rank_zero_deprecation(
-    "`pytorch_lightning.metrics.*` module has been renamed to `torchmetrics.*` and split off to its own package"
-    " (https://github.com/PyTorchLightning/metrics) since v1.3 and will be removed in v1.5"
-)