bpo-46470: remove unused branch from typing._remove_dups_flatten (GH-30780)

The branch was a remnant of old 3.6 typing.Union implementation.

Author: sobolevn

Lib/typing.py

@@ -280,8 +280,6 @@ def _remove_dups_flatten(parameters):
     for p in parameters:
         if isinstance(p, (_UnionGenericAlias, types.UnionType)):
             params.extend(p.__args__)
-        elif isinstance(p, tuple) and len(p) > 0 and p[0] is Union:
-            params.extend(p[1:])
         else:
             params.append(p)
 

Misc/NEWS.d/next/Library/2022-01-22-13-17-35.bpo-46470.MnNhgU.rst

@@ -0,0 +1 @@
+Remove unused branch from ``typing._remove_dups_flatten``