Regular FirefoxCI Taskcluster upgrade cadence starting Wednesday, April 20

[Aki Sasaki]

The Taskcluster, CloudOps, and Releng teams will begin rolling out minor Taskcluster releases to the FirefoxCI cluster at a regular cadence, every two weeks, starting this Wednesday, April 20. As with the previous minor version upgrades, we will not close trees, but instead:

- Verify with Relman before proceeding
- Upgrade the cluster at 3pm UTC / 8am PDT
- Finish by 3:30pm UTC / 8:30am PDT; respond to this email.

There is now a calendar, and we will keep notifying this list in advance.

Please let us know if you have any questions or concerns.

Backchannels:
- Slack: #firefox-ci-proj (primary) and #taskcluster-cloudops
- Matrix: #releaseduty and #firefox-ci