Cleanup the labels as they seem to correlate with each other, not used correctly or used insufficiently because users forget to apply all the appropriate labels

[viktor-yunenko]

I would recommend to keep only the labels that are helpful for the issues processing.

• Product Emergency - no open issues, highly correlates with High Priority since they imply the same idea I guess?
• Database - that one hasn't been used correctly in the last years (at least not according to its description), but even if it had it seems to include too many issues to be helpful during filtering?
• `In progress - no open issues, and we're using the boards now
• Stability seems to mean the same as Velocity and Code Quality, hence users often forgot to use them where appropriate and used eg only Velocity but not Code Quality, ie now it doesn't really help anymore. Could we merge them perhaps?
• Product Decision seems as it has the same meaning as UX?

@sebgrebe, @vagarwalla, what do you think?