Remove dead code (#8168)

The `in` operator is handled by `visit_comparison_expr`.

Author: JukkaL

mypy/checkexpr.py

@@ -2070,10 +2070,6 @@ def visit_ellipsis(self, e: EllipsisExpr) -> Type:
 
     def visit_op_expr(self, e: OpExpr) -> Type:
         """Type check a binary operator expression."""
-        if e.op == 'in':
-            self.accept(e.right)
-            self.accept(e.left)
-            return self.bool_type()
         if e.op == 'and' or e.op == 'or':
             return self.check_boolean_op(e, e)
         if e.op == '*' and isinstance(e.left, ListExpr):