Default labels conflict with Dependabot

[jwodder]

Some of the default labels created by auto — namely, "major", "minor", and "patch" — happen to have special meaning to Dependabot. Whenever Dependabot creates a pull request for a major version update (e.g., updating a dependency from v3 to v4), if the repository the PR is created in has a "major" label defined, Dependabot will apply the "major" label to that PR (and likewise for "minor" and "patch"), which will affect the version bump level calculated by auto, likely in a way that the user does not want. There is currently no way to stop Dependabot from doing this, so the next best thing would be for auto to change its default labels to something that doesn't have meaning to Dependabot. For example, for some of our projects, we use "semver-major", "semver-minor", and "semver-patch".

[divikshrivastava]

Can I take a stab at this ? @jwodder