I can't really think why this would not be a good idea:
I would say, let's first flush out what these tags mean to the site by having someone write a wiki summary for both tags (or at least propose what the tag should mean for the site in an answer here). Unless we have a good reason to keep them, let's just clean up the questions and let the nightly unused tag culling put them both out of their misery.
What sort of questions should be collected under https://apple.stackexchange.com/questions/tagged/administrator and what sort of questions should be collected under https://apple.stackexchange.com/questions/tagged/admin
We could merge and then clean up later as it appears both tags suffer from vague use patterns.