Update smoke tests to use both Rack 2 and 3

.github/workflows/tests.yml

@@ -24,6 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby_version: ["3.0", "3.1", "3.2", "3.3"]
+        rack_version: ["~> 2", "~> 3"]
     runs-on: ubuntu-latest
     services:
       postgres:
@@ -51,7 +52,12 @@ jobs:
         uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
-          ruby-version: "${{ matrix.ruby-version }}"
+          ruby-version: "${{ matrix.ruby_version }}"
+      - name: Update Gemfile for Rack version
+        run: |
+          echo 'gem "rack", "${{ matrix.rack_version }}"' >> Gemfile
+      - name: Install Dependencies
+        run: bundle install
       - name: Start bin/que
         run: |
           bundle exec bin/que ./lib/que.rb --metrics-port=8080 --ci