REFACT: remove unnecessary change of sort from True to None

Author: AlexKirko

pandas/core/indexes/api.py

@@ -214,10 +214,6 @@ def conv(i):
             return result.union_many(indexes[1:])
         else:
             for other in indexes[1:]:
-                # GH 35092. Pass sort to Index.union
-                # Index.union expects sort=None instead of sort=True
-                if sort:
-                    sort = None
                 result = result.union(other, sort=sort)
             return result
     elif kind == "array":