fixing docker-image.yml.

Author: Felipe Almeida Baccaro

.github/workflows/docker-image.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: true
-      max-parallel: 2
+      max-parallel: 4
       matrix:
         version: [ 8.3,8.4, 8.5 ]
         sapi: [ cli, fpm ]