Ruby

Revert r35443.

Revert "* test/rubygems/test_gem_installer.rb: fix broken test for r35541."

• r35541 breaks exist tests, it should be a bug unless it is inteneded.
  there seems no such intention.
  https://github.com/seattlerb/minitest/commit/68858105b2eb11c85105ffac5f32b662c59397f3
• assert('mswin32' =~ Gem::Platform.local) won't output any useful
  information when it fails.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35544 b2dd03c8-39d4-4d8f-98ff-823fe69b080e