Revert "ci: run tests in parallel with Testcontainers MySQL"

Paratest's per-process DB suffix (testing_test_N) conflicts with the
Testcontainers user permissions (only 'testing' DB granted). Restore
the mysql service + sequential pest run. Parallel + per-process DBs
needs a separate change: either widen container grants or override
Laravel ParallelTesting::setUpProcess to no-op.

.github/workflows/ci.yml

@@ -70,6 +70,15 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     needs: build-assets
+    services:
+      mysql:
+        image: mysql:8.0
+        env:
+          MYSQL_ROOT_PASSWORD: password
+          MYSQL_DATABASE: testing
+        ports:
+          - 3306:3306
+        options: --health-cmd="mysqladmin ping" --health-interval=10s --health-timeout=5s --health-retries=3
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -108,9 +117,15 @@ jobs:
         run: php artisan key:generate
 
       - name: Tests
-        run: ./vendor/bin/pest --exclude-testsuite=Browser,Performance --parallel --processes=4
+        run: ./vendor/bin/pest --exclude-testsuite=Browser,Performance
         env:
-          TESTCONTAINERS: true
+          TESTCONTAINERS: false
+          DB_CONNECTION: mysql
+          DB_HOST: 127.0.0.1
+          DB_PORT: 3306
+          DB_DATABASE: testing
+          DB_USERNAME: root
+          DB_PASSWORD: password
 
   browser-tests:
     if: github.event_name == 'pull_request'