Update WP version in workflow

Author: mukeshpanchal27

.github/workflows/php-test-plugins.yml

@@ -46,7 +46,7 @@ jobs:
         coverage: [false]
         include:
           - php: '7.4'
-            wp: '6.5'
+            wp: '6.6'
           - php: '8.3'
             wp: 'trunk'
           - php: '8.2'