Remove v7.x labels

[targos]

The v7.x branch is unsupported. I'd like to remove related labels: backported-to-v7.x, dont-land-on-v7.x and v7.x.
Any objection?

[cjihrig]

SGTM

[joyeecheung]

Not really object to this but I think they could be useful for archaeological purpose?

[joyeecheung]

(^ although, the labeling event itself is recorded in the thread

[fhinkel]

SGTM

[mhdawson]

SGTM

[refack]

Not really object to this but I think they could be useful for archaeological purpose?

AFAIR they are not removed from existing issues, just from the dropdown for adding to new issues.
so 👍

[maclover7]

While doing this, should figure out what to do (if anything) with the three open issues that are still tagged v7.x.

[targos]

I closed the one issue that affected only v7.x (#9707). Both other issues also affect at least v6.x.

[targos]

Done