cannot auto-merge PRs

[iliapolo]

The build-and-integ workflow is blocking the merge, waiting for a member of the CDK team to approve it. We should add an exemption for automated PRs.

The workflow is blocking because it runs in the integ-approval environment, which must be manually approved. There's no good way to bypass the approval step automatically, so the only other thing to do is to make it so that upgrade PRs run the workflow in an environment without approval. Since this might be a security concern I am not yet taking this approach before I get confirmation from the rest of the team that it is ok.