change(release): Only allow releases from the main branch, and update workflow names

[teor2345]

Motivation

1. We could accidentally release from any branch, but we only want to release from main
2. Some of the workflow names have changed, so they need to be updated in the release template

PR Author Checklist

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• Will the PR name make sense to users? Internal PR
• Does the PR have a priority label?
• Have you added or updated tests?
• Is the documentation up to date?

Not a significant change.

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Specifications

https://github.com/crate-ci/cargo-release/blob/master/docs/reference.md#config-fields

Solution

1. Configure cargo release to only release from main (it exits with an error for any other branch)
2. Update workflow links

Testing

I manually tested releasing from another branch fails, and I tested the links.

Review

This is a low priority cleanup.

Reviewer Checklist

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• Does the PR scope match the ticket?
• Are there enough tests to make sure it works? Do the tests cover the PR motivation?
• Are all the PR blockers dealt with?
  PR blockers can be dealt with in new tickets or PRs.

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