Update information about the Bitbucket Cloud issue tracker

Merged username-removed-7808 requested to merge belak/www-gitlab-com:patch-214 into master

Bitbucket Cloud has an issue tracker, though it doesn't have as many features as Gitlab's. I've updated the website to reflect this, though I can make any wording changes if anyone who actually works at Gitlab has preferences.

Arguably this could be split into two lines, one to say there's an issue tracker and another talking about advanced features. So I went with the middle ground and fixed the text and set it to "sortof".