Update prep-release workflow

[svetlanabrennan]

This repo is using the old way of prepping a release that requires updating the release notes.

Need to update the prep release workflow to use the correct workflow like we do in the node agent repo.

newrelic/node-newrelic-aws-sdk#232

Update Pull Requests settings in Settings > General to squash merges, use PR title and delete head branches

[workato-integration]

https://new-relic.atlassian.net/browse/NR-255522