Only show notoken as possible API error once

Currently notoken is being listed as possible
API error twice if it's explicitly set as
required parameter and needsToken() returns
true.

See:
https://www.wikidata.org/w/api.php?action=paraminfo&modules=edit

Change-Id: Ia17c5cfa634919b43affa146df0d1dc0ff06b758
Merge "Only show notoken as possible API error once"