Unset BUNDLE_GEMFILE after setup

Author: ur5us

.github/workflows/main.yml

@@ -46,9 +46,8 @@ jobs:
           ruby-version: ${{ matrix.ruby_version }}
       - name: Build and run test
         run: |
-          gem update bundler
-          bundle -v
-          bundle
+          bundle install
+          unset BUNDLE_GEMFILE
           bundle exec appraisal rails_${{ matrix.rails_version }} bundle
           bundle exec appraisal rails_${{ matrix.rails_version }} rake