As people have explained in the comments, that tag might not be appropriate for Super User. If you were going to create it (and I would suggest based on those comments that you don't), you could deal with the length limit by partially abbreviating it, e.g. vs-team-services. The tag wiki excerpt would then clarify what exactly the tag is about, and people would likely associate Visual Studio with the phrase "team services", whereas I wouldn't immediately have a guess about vsts.
Also, the reason you're receiving that error message is that tags differing only in hyphenation or capitalization are no longer allowed. If I understand correctly, only moderators can create tags that would be blocked by that check (there are legitimate exceptions to the rule, like windows and window).
