test(rubygems): Simplify tests (#23521)

...s/datasource/rubygems/__fixtures__/dependencies-rails.dat

lib/modules/datasource/rubygems/__fixtures__/rails/info.json

...ules/datasource/rubygems/__fixtures__/rails/versions.json

...modules/datasource/rubygems/__fixtures__/rubygems-org.txt

...ules/datasource/rubygems/__snapshots__/index.spec.ts.snap

lib/modules/datasource/rubygems/index.spec.ts

lib/modules/datasource/rubygems/schema.spec.ts

package.json

yarn.lock