[rubygems/rubygems] Fix daily CI

Platform specific versions of ffi-1.17.2 are not compatible with Ruby
3.5, so Bundler fails to resolve in Ruby 3.5 using recorded VCR
responses.

Use the generic version of ffi-1.17.2, which should work for all rubies,
consistently to fix that.

https://github.com/rubygems/rubygems/commit/a192f7e35d

spec/bundler/realworld/ffi_spec.rb

@@ -47,7 +47,7 @@ RSpec.describe "loading dynamically linked library on a bundle exec context", re
     install_gemfile <<-G
       source "https://rubygems.org"
 
-      gem 'ffi'
+      gem 'ffi', force_ruby_platform: true
     G
 
     bundle "exec ruby foo.rb"