CI workaround for PHP < 7.4 & MySQL 8

The error on PHP 7.2 & 7.3 is:

> PDO::__construct(): The server requested authentication method unknown to the client [caching_sha2_password]

See:
- https://stackoverflow.com/q/53066962/569101
- https://stackoverflow.com/q/52364415/569101
- https://stackoverflow.com/q/51489616/569101
- https://stackoverflow.com/q/50026939/569101

Also upgrade `actions/checkout` v3

.github/workflows/assets.yml

@@ -14,7 +14,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v3"
 
       - name: "Install Node"
         uses: actions/setup-node@v2