Use ubuntu18.04

Author: driesvints

.github/workflows/tests.yml

@@ -8,15 +8,15 @@ on:
 
 jobs:
   tests:
+    runs-on: ubuntu-18.04
 
-    runs-on: ubuntu-latest
     strategy:
       fail-fast: true
       matrix:
         php: [7.3, 7.4, 8.0]
         laravel: [^8.0]
 
-    name: P${{ matrix.php }} - L${{ matrix.laravel }}
+    name: PHP ${{ matrix.php }} - Laravel ${{ matrix.laravel }}
 
     steps:
       - name: Checkout code