fix: Allow multiple audiences for id_token.verify_token (#733)

* feat: Allow multiple audiences for id_token.verify_token (#732)

* running black

Co-authored-by: arithmetic1728 <58957152+arithmetic1728@users.noreply.github.com>
diff --git a/google/oauth2/id_token.py b/google/oauth2/id_token.py
index 5e36260..5fbb6a1 100644
--- a/google/oauth2/id_token.py
+++ b/google/oauth2/id_token.py
@@ -112,8 +112,8 @@
         id_token (Union[str, bytes]): The encoded token.
         request (google.auth.transport.Request): The object used to make
             HTTP requests.
-        audience (str): The audience that this token is intended for. If None
-            then the audience is not verified.
+        audience (str or list): The audience or audiences that this token is
+            intended for. If None then the audience is not verified.
         certs_url (str): The URL that specifies the certificates to use to
             verify the token. This URL should return JSON in the format of
             ``{'key id': 'x509 certificate'}``.