Revert "Test installing rake to check RubyGems recognizes the executable as safe to override"

* This reverts commit 35f0af3.
* It fails for some cases like Ruby <= 2.2 and on some RubyInstaller builds,
  see #98 (comment)
* Most users will use Bundler to install rake, and that already works fine.

Author: eregon

.github/workflows/test.yml

@@ -100,9 +100,6 @@ jobs:
       if: startsWith(matrix.os, 'windows') && startsWith(matrix.ruby, 'jruby')
       run: gem install sassc -N
 
-    - name: Test installing rake to check RubyGems recognizes the executable as safe to override
-      run: gem install rake
-
   lint:
     runs-on: ubuntu-latest
     steps: