Update MAINTAINERS.md release instructions

[JonZeolla]

Summary of the issue

We have some missing instructions in the MAINTAINERS.md. You need to run pipenv install --deploy --ignore-pipfile --dev in order to setup your environment, and you need to push to a feature branch and open a PR for releases because we have a branch policy that prevents directly pushing to main.

Also, currently the instructions have you push the v tag to the feature branch, but we don't want this. It should only get pushed to the main branch.