Change authentication string

- according to documentation, I'm supposed to prepend "token". However,
  swagger doesn't do that. They both do seem to work (i.e. they
  authenticate correctly), but adding "token " has a strange performance
  penalty.

gitea-to-ics.py

@@ -20,8 +20,7 @@ def get_combined(token):
         req = urllib.request.Request(GITEA_REPO_URL
                                 + f"/repos/issues/search?state=open&{q}=true")
         req.add_header("Accept", "application/json")
-        req.add_header("Content-Type", "application/json")
-        req.add_header("Authorization", "token " + token)
+        req.add_header("Authorization", token)
 
         timestamp=datetime.datetime.now()
         print(f"{timestamp} Requesting and parsing {q}")