Bump premailer from 3.7.0 to 3.8.0 in /requirements (#16955)
Bump premailer from 3.7.0 to 3.8.0 in /requirements (#16955)

Bumps [premailer](https://github.com/peterbe/premailer) from 3.7.0 to 3.8.0.
- [Release notes](https://github.com/peterbe/premailer/releases)
- [Changelog](https://github.com/peterbe/premailer/blob/master/CHANGES.rst)
- [Commits](https://github.com/peterbe/premailer/commits)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
diox/olympia,wagnerand/addons-server,mozilla/addons-server,mozilla/olympia,bqbn/addons-server,mozilla/olympia,mozilla/olympia,mozilla/addons-server,bqbn/addons-server,mozilla/addons-server,mozilla/olympia,diox/olympia,diox/olympia,bqbn/addons-server,bqbn/addons-server,wagnerand/addons-server,mozilla/addons-server,wagnerand/addons-server,diox/olympia,wagnerand/addons-server