Fix typing for legacy Python

Author: jschlyter

src/cryptojwt/utils.py

@@ -8,7 +8,7 @@
 import warnings
 from binascii import unhexlify
 from email.message import EmailMessage
-from typing import List
+from typing import List, Set, Union
 
 from cryptojwt.exception import BadSyntax
 
@@ -262,7 +262,7 @@ def httpc_params_loader(httpc_params):
     return httpc_params
 
 
-def check_content_type(content_type: str, mime_type: str | list[str] | set[str]):
+def check_content_type(content_type: str, mime_type: Union[str, List[str], Set[str]]):
     """Return True if the content type contains the MIME type"""
     msg = EmailMessage()
     msg["content-type"] = content_type