Fix F.resolve_expression() return type (#1659)

Co-authored-by: Marti Raudsepp <marti@juffo.org>

Author: schinckel

django-stubs/db/models/expressions.pyi

@@ -133,7 +133,7 @@ class F(Combinable):
         reuse: set[str] | None = ...,
         summarize: bool = ...,
         for_save: bool = ...,
-    ) -> F: ...
+    ) -> Expression: ...
     def replace_expressions(self, replacements: Mapping[F, Any]) -> F: ...
     def asc(
         self,