Remove bundle exec for assert_separately.

  https://github.com/ruby/cgi/actions/runs/3561473520/jobs/5982415938

Author: hsbt

.github/workflows/test.yml

@@ -38,4 +38,4 @@ jobs:
         ruby-version: ${{ matrix.ruby }}
         bundler-cache: true # 'bundle install' and cache gems
     - name: Run test
-      run: bundle exec rake test
+      run: rake test