build(deps): bump codecov from 0.2.7 to 0.2.8 in /Library/Homebrew

Call `clear_available_cache` after installing Git.

Bumps [codecov](https://github.com/codecov/codecov-ruby) from 0.2.7 to 0.2.8.
- [Release notes](https://github.com/codecov/codecov-ruby/releases)
- [Changelog](https://github.com/codecov/codecov-ruby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/codecov/codecov-ruby/compare/v0.2.7...v0.2.8

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Remove `os/linux/diagnostic`.

Move `command_help_lines` into `Help` module.

Refactor and document `Svn`.

Refactor and document `Git`.

sorbet: update RBI files using Tapioca.

Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/tapioca.yml).

Refactor and document `Bottles`.

Refactor and document `Inreplace`.

Refactor and document `Help`.

Refactor and document `Hardware`.

Refactor and document `SystemConfig`.

sorbet: update RBI files using Tapioca.

workflows/tapioca: reset earlier

Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/tapioca.yml).

workflows/tapioca: fix it really

sorbet: update RBI files using Tapioca.

readme: Update maintainer list

Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/tapioca.yml).

- In all of the PRs that this Action triggered, the `tapioca-update`
  branch was >200 commits behind the latest `master`.
- As per https://github.com/Homebrew/brew/pull/8435#issuecomment-678546024,
  we shouldn't rely on the `Homebrew/actions/setup-homebrew` master
  (the `origin/master` ref) branch being up to date, so resetting to
  `origin/master` was a bad idea.
- A side effect of this is that when we raise PRs to change the Action,
  the PRs that it generates will include local commits. But functionally
  all we care about is the Action that runs on a schedule.

pr-pull: require formula

This caused bottle publishes to think that no bottles were needed.