Update stubs/httpretty/httpretty/core.pyi

Co-authored-by: Semyon Moroz <donbarbos@proton.me>

Author: adamtheturtle

stubs/httpretty/httpretty/core.pyi

@@ -76,7 +76,7 @@ class Entry(HttpBaseClass):
     ) -> None: ...
     def validate(self) -> None: ...
     def normalize_headers(self, headers: _Headers) -> dict[str, str]: ...
-    def fill_filekind(self, fk: Any) -> None: ...
+    def fill_filekind(self, fk: _WritableFileobj) -> None: ...
 
 class URIInfo(HttpBaseClass):
     default_str_attrs: tuple[str, ...]