Preflight - Teleport

Preflight Checklist

This checklist is to be run prior to cutting the release branch.

Update VERSION in Makefile to next dev tag
Send out a call to #teleport-dev on slack for people to search code for DELETE IN and REMOVE IN comments and clean up if appropriate
Update the CI buildbox image
- Update the BUILDBOX_VERSION in build.assets/images.mk. Commit and merge.
- Update e/.github/workflows/build-buildboxes-cron.yaml to uncomment final pre-release job and ensure it has the correct branch names (two places). Commit and merge.
- After the BUILDBOX_VERSION update in the build.assets/images.mk has merged to master, build the buildboxes for the next BUILDBOX_VERSION. The first run will build the "assets" buildbox and the other builds will likely fail. Run again after the first has finished to build the others that use the "assets" buildbox:
```
today=$(LOCALE=C TZ=UTC date +%A)
gh workflow run --repo gravitational/teleport.e --field assets-day="${today}" build-buildboxes.yaml
gh workflow run --repo gravitational/teleport.e build-buildboxes.yaml
```
- Update all the CI jobs in .github/workflows that use teleport-buildbox:teleportX and teleport-buildbox-centos7:teleportX-amd64 and bump X to the new version.
- Update all the CI jobs in e/.github/workflows that use teleport-buildbox:teleportX and bump X to the new version.