[coreboot] Planned maintenance on Thu Dec 21 8:00 - 10:00 UTC

[Felix Singer]

Our hoster made a mistake during the last maintenance this week and it
needs to be fixed. That requires another (but last!) downtime at the
following time for two hours.

Start of maintenance:

Thursday, Dec 21 8:00 UTC

Expected end of maintenance:

Thursday, Dec 21 10:00 UTC

We are sorry for the inconveniences.

Felix