fix: choose branch instead of prBranch when noCi is true

[dcneiner]

Resolves #1596

Open to any feedback on this PR, including if it is not a good change for the project and just needs to be closed.

Question on the tests: I started to add a new test for the change, but found an existing assertion that prior to #1521 seemed to be verifying noCi wouldn't reject even if isPr were true. Was the change I made sufficient or would you like a separate test for this use case?

This also has me wondering if there should/could be another way to provide what semantic-release uses as the branch for any situations where inferring it from envCi may not provide the correct answer?

[dcneiner]

The more I think and look at this, I'm beginning to think the issue may be in env-ci when used on Github Actions. And given a recent fix in semantic-release-github-pr I think my changes will just make matters worse. I'm sorry I didn't come to this understanding prior to opening the issue and PR.