update testing matrix

Author: Tom Schlick

.github/workflows/tests.yml

@@ -24,7 +24,9 @@ jobs:
             fail-fast: true
             matrix:
                 php: [7.3, 7.4, 8.0]
-                stability: [prefer-lowest, prefer-stable]
+                stability: 
+#                   - prefer-lowest
+                  - prefer-stable
 
         name: PHP ${{ matrix.php }} - ${{ matrix.stability }}