fix: dormant usernames guidelines to be factual

Little background, one year ago I started using Gitlab at Virtkick and now we are starting to use it at Tenfold. I found the official guideline on taking over usernames and went through it. Long story short, I was not able to get any reply from support even though I pinged it 4 times.

As you can see I tried numerous times to get an answer. My PR fixes the process to match reality.

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