Update tests workflow for GitHub Actions

Author: divineniiquaye

.github/workflows/tests.yml

@@ -1,5 +1,6 @@
 name: Tests
 on: [push, pull_request]
+
 jobs:
   build:
     strategy:
@@ -12,7 +13,8 @@ jobs:
           - php: "8.0"
             coverage: "false"
             composer-flags: "--ignore-platform-req=php"
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
+
     steps:
       - name: Checkout
         uses: actions/checkout@v2