Update bundler dependency to be more flexible

[KrauseFx]

Fixes #7963

[endocrimes]

LGTM

[summera]

@KrauseFx possible to go lower than 1.12? For example: ~> 1.0?

[KrauseFx]

@summera Why? We haven't tested it with a lower version, we use the bundler API directly when the user has plugins enabled for their project.

[summera]

Got it. So is >= 1.12 required for fastlane plugins to work or you're unsure?

I'm in a situation where the default bundler version in my AWS Elastic Beanstalk environment is lower than 1.12 (1.9.6). So I'm wondering if it's possible to make the requirement less strict by allowing lower versions of bundler for people in similar situations.

[KrauseFx]

@summera I'm unsure, I haven't tested it below that version, that's why we require it. If you can try using it with an older version, and make sure plugin installation and adding new plugins work, I'm ok with reducing the minimum version more 👍

[KrauseFx]

We can merge this for now, as it's already an improvement like this 👍

[summera]

@KrauseFx Cool sounds good 👍 . I'll get back to you on reducing the min version. Thanks again!

[KrauseFx]

Thanks 👍