Fix php.yml (laravel-notification-channels#105)

Author: shahvirag

.github/workflows/php.yml

@@ -34,7 +34,3 @@ jobs:
         run: |
             composer require --dev --no-interaction "orchestra/testbench:^5.1"
             composer test:integration
-        if: matrix.laravel-version == '^8.0'
-            run: |
-                composer require --dev --no-interaction "orchestra/testbench:^6.0"
-                composer test:integration