Remove runtime dependency on base64

[Earlopain]

Ruby 3.3 shows a warning when using base64 without declaring it in the gemspec. Ruby 3.4 will remove base64 as a default gem.

Since this gem is only using a single method in one place there is no need to pull in the full dependency. It is only a wrapper over Array#pack.

Alternative to #1041

Other gems have taken the same/similar approach:

• [Fix #12310] Drop base64 gem from runtime dependency rubocop/rubocop#12313
• Remove base64 dependency rack/rack#2110
• Remove runtime dependency on base64 newrelic/newrelic-ruby-agent#2378
• Remove runtime dependency on base64 lostisland/faraday#1541 (pending)

[mattbrictson]

As of 2 weeks ago, it looks like Ruby head has now removed the default base64 gem entirely. So projects that use webmock fail with this exception:

/home/runner/.rubies/ruby-head/lib/ruby/3.4.0+0/bundled_gems.rb:74:in `require': cannot load such file -- base64 (LoadError)

A workaround exists: any project using webmock also has to add base64 to their Gemfile. Still, it would be nice to see this PR merged. Thanks! 🙏

[bblimke]

@Earlopain thank you for providing this solution. I appreciate the simplicity! 👍 It's great to have a solution that doesn't require adding another dependency to the gemspec.