Fix partitioned cookie handling in load_json()

Add "partitioned" to the boolean attribute check in load_json()
so it is restored as True (bool) rather than "true" (string)
on Python 3.14+ where Morsel._reserved includes partitioned.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: YuvalElbar6

aiohttp/cookiejar.py

@@ -247,7 +247,7 @@ def load_json(self, file_path: PathLike) -> None:
                         "coded_value",
                     ):
                         attr_val = morsel_data[attr]
-                        if attr in ("secure", "httponly"):
+                        if attr in ("secure", "httponly", "partitioned"):
                             morsel[attr] = True if attr_val == "true" else attr_val  # type: ignore[assignment]
                         else:
                             morsel[attr] = attr_val