Update mysql Docker tag to v8

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-20.04
     services:
         mysql:
-            image: mysql:5.7
+            image: mysql:8.3
             ports:
               - 3306:3306
             options: --health-cmd="mysqladmin ping" --health-interval=10s --health-timeout=5s --health-retries=3