Add missing defaults to third-party stubs (#14617)

stubs/setuptools/setuptools/_distutils/filelist.pyi

@@ -9,7 +9,7 @@ class FileList:
     files: list[str]
     def __init__(self, warn: Unused = None, debug_print: Unused = None) -> None: ...
     def set_allfiles(self, allfiles: Iterable[str]) -> None: ...
-    def findall(self, dir: StrPath = ...) -> None: ...
+    def findall(self, dir: StrPath = ".") -> None: ...
     def debug_print(self, msg: object) -> None: ...
     def append(self, item: str) -> None: ...
     def extend(self, items: Iterable[str]) -> None: ...