target laravel 8 only

Author: michaeldyrynda

.github/workflows/run-tests.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         php: [7.4, 7.3]
-        laravel: [^7.0, ^8.0]
+        laravel: [^8.0]
         dependency-version: [prefer-lowest, prefer-stable]
         os: [ubuntu-latest, windows-latest]