Do not test for Symfony 6.4 with PHP 7.4

as Symfony 6.4 needs PHP 8.1 or greater.

Author: relthyg

.github/workflows/tests.yml

@@ -27,9 +27,6 @@ jobs:
           -
             php: '8.4'
             dependencies: highest
-          -
-            php: '7.4'
-            symfony: '6.4.*'
           -
             php: '8.1'
             symfony: '6.4.*'