Fix various pos-only stubtest complaints previously allowlisted (#7228)

stdlib/io.pyi

@@ -181,3 +181,4 @@ class IncrementalNewlineDecoder(codecs.IncrementalDecoder):
     def decode(self, input: bytes | str, final: bool = ...) -> str: ...
     @property
     def newlines(self) -> str | tuple[str, ...] | None: ...
+    def setstate(self, __state: tuple[bytes, int]) -> None: ...