Releases are triggered by code review

[BigLep]

Done Criteria

1. The release steps outlined in https://github.com/filecoin-project/builtin-actors#releasing can be followed without requiring manual clicking in the GitHub UI. Instead, releases should occur as a result of an approved PR.
2. The release description should be populated with the GitHub-generated release notes.

Why Important

The release process in https://github.com/filecoin-project/builtin-actors#releasing doesn't have any peer review. Mistakes can get made. Mistagging has happened in the past and can't be reverted. This is usually fixed by just doing another release, but this adds unnecessary confusion.

User/Customer

Maintainers

Notes

1. This is not a standard Rust repo. We don't publish to crates.io.

[BigLep]

This was closed by #1571