Fixed broken json_client (#17529)

The json_client depends on httpx and thus the response doesn't contain
the attribute 'ok'. In consequence, the missing attribute has been changed
to is_error.

closes: #17527

Co-authored-by: Szymon Wojciechowski <szymon.wojciechowski@here.com>
(cherry picked from commit fbddefe)

airflow/api/client/json_client.py

@@ -32,7 +32,7 @@ def _request(self, url, method='GET', json=None):
         if json is not None:
             params['json'] = json
         resp = getattr(self._session, method.lower())(**params)
-        if not resp.ok:
+        if resp.is_error:
             # It is justified here because there might be many resp types.
             try:
                 data = resp.json()