Merge remote-tracking branch 'mypypy/narrowing/move_join_based_narrowing_towards_union_based_narrowing' into narrowing/move_join_based_narrowing_towards_union_based_narrowing

Author: tyralla

mypy/binder.py

@@ -6,7 +6,6 @@
 from typing_extensions import TypeAlias as _TypeAlias
 
 from mypy.erasetype import remove_instance_last_known_values
-from mypy.join import join_simple
 from mypy.literals import Key, literal, literal_hash, subkeys
 from mypy.nodes import Expression, IndexExpr, MemberExpr, NameExpr, RefExpr, TypeInfo, Var
 from mypy.subtypes import is_same_type, is_subtype