chore: remove deprecated workflow files from v1.x (#1115)

- Remove dependabot.yml (deprecated)
- Remove test.yml workflow (consolidated into CI)
- Remove lint.yml workflow (consolidated into CI)
- Remove types.yml workflow (consolidated into CI)

These workflows were already removed from main branch and are showing
as disabled in GitHub Actions UI. Removing from v1.x branch to clean
up the Actions workflow list.

Author: jdalton