[Musixmatch] Handle non-200 status code

Musixmatch returns
```
{'message': {'header': {'status_code': 401, 'execute_time': 0.0026848316192627, 'hint': 'captcha'}, 'body': []}}
```
after some requests, currently we return None to pass to the next provider, until we find a solution.
Fixes #35

syncedlyrics/providers/musixmatch.py

@@ -116,6 +116,10 @@ def get_lrc(self, search_term: str) -> Optional[str]:
                 ("quorum_factor", "1.0"),
             ],
         )
+        status_code = r.json()["message"]["header"]["status_code"]
+        if status_code != 200:
+            self.logger.warning(f"Got status code {status_code} for {search_term}")
+            return None
         body = r.json()["message"]["body"]
         tracks = body["track_list"]
         cmp_key = lambda t: f"{t['track']['track_name']} {t['track']['artist_name']}"