Update pandas-stubs/core/frame.pyi

Co-authored-by: Irv Lustig <[email protected]>

Author: loicdiridollou

pandas-stubs/core/frame.pyi

@@ -1329,7 +1329,7 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
     def stack(
         self,
         level: IndexLabel = ...,
-        future_stack: Literal[True] = ...,
+        future_stack: Literal[True],
     ) -> Self | Series: ...
     @overload
     def stack(