net/traefik: Update to upstream version 2.7.0
Details:
- New release on the 2.7 branch, see https://github.com/traefik/traefik/releases/tag/v2.7.0
- Configuration files are compatible with 2.6.1 and later, no breaking changes went into the new branch, see https://github.com/traefik/traefik/releases/tag/v2.7.0
MFH: 2022Q2