Reminder: Beta freeze and code complete deadline in one week

[Ben Cotton]

According to the Fedora 30 schedule[1], the 100% code complete
deadline[2] for Changes is Tuesday, 5 March. The beta freeze[3]
takes effect on this date as well. All Changes should be in "ON_QA"
state by then.

[1] https://fedoraproject.org/wiki/Releases/30/Schedule
[2] https://fedoraproject.org/wiki/Changes/Policy#Change_Checkpoint:_100.25_code...
[3] https://fedoraproject.org/wiki/Milestone_freezes