Fix `depends_on` deprecation
Fix `depends_on` deprecation

Updates git Homebrew formula to use a string for the perl `depends_on`
and resolves the following error message during runs.

```
Warning: Calling 'depends_on :perl' is deprecated!
Use 'depends_on "perl"' instead.
/usr/local/Library/Taps/boxen/homebrew-brews/git.rb:38:in `<class:Git>'
Please report this to the boxen/brews tap!
```

boxen/puppet-git,boxen/puppet-git