build: bump rspec-expectations from 3.8.5 to 3.8.6 in /Library/Homebrew

Bumps [rspec-expectations](https://github.com/rspec/rspec-expectations) from 3.8.5 to 3.8.6.
- [Release notes](https://github.com/rspec/rspec-expectations/releases)
- [Changelog](https://github.com/rspec/rspec-expectations/blob/master/Changelog.md)
- [Commits](https://github.com/rspec/rspec-expectations/compare/v3.8.5...v3.8.6

)

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