Simplify pip requirements files

[ferrarimarco]

Fixes #3727

Proposed Changes

1. Remove transitive dependencies of each linter from pip requirements files. We now rely on each linter to install its own dependencies. This will reduce the number of dependency updates to take care of, and reduce the number of failing builds due to dependency conflicts. It may also make the image somewhat smaller because some of these transitive dependencies were dropped by their upstreams, and not needed anymore.
2. Remove two dependency update scripts that we don't need anymore.
3. Fix a couple of typos in a comment.

Readiness Checklist

Author/Contributor

• If documentation is needed for this change, has that been included in this pull request

Reviewing Maintainer

• Label as breaking if this is a large fundamental change
• Label as either automation, bug, documentation, enhancement, infrastructure, or performance

[zkoppert]

✨ Thanks for taking this on!! 🎉