Sunset metrics-team mailing list

We moved the former metrics team into the network-health one and decided that we can therefore sunset the metrics-team mailing list.

This is the parent ticket for discussing the detailed plan and keeping track of the progress of the related child tasks.

• Give 2 weeks notice to subscribers of metrics-team@ mailing list about what is going to happen.
• Move all subscribers of metrics-team@ to network-health mailing list.
• tpo/network-health/metrics/collector#40015 (closed)
• tpo/network-health/metrics/onionoo#40019 (closed)
• tpo/network-health/metrics/cloud#40004 (closed)
• tpo/network-health/metrics/library#40011 (closed)
• Go over code/docs linking to the metrics list, too (e.g. https://metrics.torproject.org/about.html#contact has a reference)

/cc @hiro