Add MRI Ruby 3.4 support

[a1flecke]

MRI Ruby was released in December of 2024. This buildpack does not currently support it

Describe the Enhancement

I would like the MRI Ruby buildpack to be able to install Ruby 3.4

Possible Solution

It looks like this MR was trying to add this support

Motivation

We have multiple Rails apps running on buildpacks that are not able to update to Ruby 3.4

[jacobthompsonramsey]

Interested in this