PyMySQL: added stub for SSCursor.readnext

stubs/PyMySQL/pymysql/cursors.pyi

@@ -45,7 +45,7 @@ class DictCursorMixin:
 
 class SSCursor(Cursor):
     def __del__(self) -> None: ...
-    def read_next(self): ...
+    def read_next(self) -> tuple[Any, ...] | None: ...
     def fetchall(self) -> list[tuple[Any, ...]]: ...  # type: ignore[override]
     def fetchall_unbuffered(self) -> Iterator[tuple[Any, ...]]: ...
     def scroll(self, value: int, mode: str = "relative") -> None: ...
@@ -54,3 +54,4 @@ class DictCursor(DictCursorMixin, Cursor): ...  # type: ignore[misc]
 
 class SSDictCursor(DictCursorMixin, SSCursor):  # type: ignore[misc]
     def fetchall_unbuffered(self) -> Iterator[dict[str, Any]]: ...  # type: ignore[override]
+    def read_next(self) -> dict[str, Any] | None: ...