Fix names for the workflows

Author: dmitry-ivanov

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
         php: [7.3, 7.4, 8.0]
         stability: [prefer-lowest, prefer-stable]
 
-    name: PHP ${{ matrix.php }} (--${{ matrix.stability }})
+    name: PHP ${{ matrix.php }} / ${{ matrix.stability }}
 
     steps:
       - name: Checkout code