Fix a SyntaxWarning caused by invalid escape sequences

The warning is thrown when Python imports the file,
and manifests in the test suite with this error:

```
jwt/api_jwt.py:326
  /home/runner/work/pyjwt/pyjwt/jwt/api_jwt.py:326: SyntaxWarning: invalid escape sequence '\*'
    (e.g. HS\* and RS\*).
```

Author: kurtmckee

jwt/api_jwt.py

@@ -323,7 +323,7 @@ def decode(
                configure it in the same place you configure the
                ``key``. Make sure not to mix symmetric and asymmetric
                algorithms that interpret the ``key`` in different ways
-               (e.g. HS\* and RS\*).
+               (e.g. HS\\* and RS\\*).
         :type algorithms: typing.Sequence[str] or None
 
         :param jwt.types.Options options: extended decoding and validation options