Missing ffi library in tests on Ruby 3.1 on Windows about fastlane

[lacostej]

Looking at the issue again. The latest rest-client release doesn't support properly the x64-mingw-ucrt platform. There's a PR from June 2022, but it hasn't been merged.

The library appears to be unmaintained. There are some forks but none that appears to be popular enough.

We should just drop the dependency on rest-client. It is only used in 2 actions, primarily due to the ability to attach files.

• fastlane/lib/fastlane/actions/mailgun.rb
• fastlane/lib/fastlane/actions/upload_symbols_to_sentry.rb

Mailgun has an official ruby library that also uses rest-client. They also want to drop the dependency. Once they do, we could maybe reuse their library. Or we rewrite the action ourselves with a different transport mechanism.

The upload_symbols_to_sentry action appears to be deprecated in favor of https://github.com/getsentry/sentry-fastlane-plugin. So we should probably just remove it.