Remove copyright dates

[SuperQ]

The CNCF copyright notice guidelines recommend against including dates/years in them.

We should, on a best effort basis, remove the year from the notice headers on our projects. This would reduce the issues with having to deal with PRs copy-and-pasting the wrong year when creating new files.

We can probably keep any date ranges for old ownership in NOTICE files.

[SuperQ]

See prometheus-community/elasticsearch_exporter#1027 for an example.

[jesusvazquez]

Another example here prometheus-community/parquet-common#7

[roidelapluie]

I approve this

[jesusvazquez]

This was approved during the last dev summit

[machine424]

Having a .git-blame-ignore-revs https://docs.github.com/en/enterprise-cloud@latest/repositories/working-with-files/using-files/viewing-and-understanding-files#ignore-commits-in-the-blame-view set up (requires a local setup as well) could help with "hiding" such formatting commits from git blame