Upgrade to isort 5 (#4323)

This now also reformats imports not at the top of files.

stdlib/3/collections/__init__.pyi

@@ -41,10 +41,7 @@ from typing import (
 from . import abc
 
 if sys.version_info >= (3, 6):
-    from typing import (
-        Collection as Collection,
-        AsyncGenerator as AsyncGenerator,
-    )
+    from typing import AsyncGenerator as AsyncGenerator, Collection as Collection
 
 _S = TypeVar("_S")
 _T = TypeVar("_T")

stdlib/3/collections/abc.pyi

@@ -29,8 +29,4 @@ from . import (
 )
 
 if sys.version_info >= (3, 6):
-    from . import (
-        Collection as Collection,
-        Reversible as Reversible,
-        AsyncGenerator as AsyncGenerator,
-    )
+    from . import AsyncGenerator as AsyncGenerator, Collection as Collection, Reversible as Reversible