fix(rainbow change): the methods (bold & white) are not on String but…

[mmotherwell]

… Rainbow

Description

Bug from the change from colorize gem to Rainbow.

Motivation and Context

I got this method running bundle_report outdated

```undefined method `bold' for an instance of String (NoMethodError)

      #{Rainbow(header.bold.white)}: released #{gem.age} (latest version, #{gem.latest_version.version}, released #{gem.latest_version.age})```

How Has This Been Tested?

Ran the test suite. Used the gem in my own gemfil.

Screenshots:

It's a small change.

I will abide by the code of conduct

[taylorrf]

I got the same error using next_rails-1.4.1 and ruby 3.3.4 and the code change proposed here fixed it for me locally. Thank you @mmotherwell

[etagwerker]

Looks good, thank you! 💯

[etagwerker]

@taylorrf @mmotherwell Just released https://rubygems.org/gems/next_rails/versions/1.4.2 with this patch. Thanks! 🙏🏼