Ruby

[rubygems/rubygems] Refactor specs to not try to remove folders that don't exist

This has the following benefits:

• Avoid duplicated work in some specs that first build a repo, and then
  overwrite it with a completely different set of gems.
• Reduce RSpec nesting and improve readability.
• The change also made surfaces several specs that were incorrect since
  they were unintentionally not testing the right thing.

https://github.com/rubygems/rubygems/commit/ed430883e0