change to the ubuntu-18.04

.github/workflows/php.yml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   run:
-    runs-on: self-hosted
+    runs-on: ubuntu-18.04
     strategy:
       matrix:
         php-versions: ['7.1', '7.2']
@@ -22,7 +22,7 @@ jobs:
         with:
           php-version: ${{ matrix.php-versions }}
         env:
-          runner: self-hosted
+          runner: ubuntu-18.04
 
       - name: Validate composer.json and composer.lock
         run: composer validate