apply_func.py: from torchtext.legacy.data import Batch (#6211)

* Update apply_func.py

The name Batch is no longer located under torchtext.data
--Error message--
File "/home/daniel/py38/lib/python3.8/site-packages/pytorch_lightning/utilities/apply_func.py", line 25, in <module>                                                      
    from torchtext.data import Batch                                                  
ImportError: cannot import name 'Batch' from 'torchtext.data' (/home/daniel/py38/lib/p
ython3.8/site-packages/torchtext/data/__init__.py)
You can fix this by changing line line 28 to:
    from torchtext.legacy.data import Batch

* Update apply_func.py

* Update apply_func.py

* Update apply_func.py

* Update apply_func.py

* Update apply_func.py

pytorch_lightning/utilities/apply_func.py

@@ -23,9 +23,13 @@
 
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from pytorch_lightning.utilities.imports import _TORCHTEXT_AVAILABLE
+from pytorch_lightning.utilities.imports import _module_available
 
 if _TORCHTEXT_AVAILABLE:
-    from torchtext.data import Batch
+    if _module_available("torchtext.legacy.data"):
+        from torchtext.legacy.data import Batch
+    else:
+        from torchtext.data import Batch
 else:
     Batch = type(None)