chore(ci): remove release epic action (#3996)

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The release EPIC action doesn't make sense anymore with the new arabica
and mocha tags. Removing it while we work on making some updates to the
release tracking.

I added the `backport:v2.x` tag to make sure any more v2 releases don't
create issues. I didn't see a backport label for v3 yet but it would be
good to apply this to that branch as well.