stdlib: add some parameter defaults (#14610)

stdlib/sre_parse.pyi

@@ -39,7 +39,7 @@ class State:
     lookbehindgroups: int | None
     @property
     def groups(self) -> int: ...
-    def opengroup(self, name: str | None = ...) -> int: ...
+    def opengroup(self, name: str | None = None) -> int: ...
     def closegroup(self, gid: int, p: SubPattern) -> None: ...
     def checkgroup(self, gid: int) -> bool: ...
     def checklookbehindgroup(self, gid: int, source: Tokenizer) -> None: ...