fix: remove 6.6 not released yet

Author: Rahe

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         operating-system: [ ubuntu-latest ]
         php-versions: [ '8.0', '8.1', '8.2', '8.3' ]
-        wp: [ '5.4', '5.5', '5.6', '5.7', '5.8', '5.9', '6.0', '6.1', '6.2', '6.3', '6.4', '6.5', '6.6', 'latest' ]
+        wp: [ '5.4', '5.5', '5.6', '5.7', '5.8', '5.9', '6.0', '6.1', '6.2', '6.3', '6.4', '6.5', 'latest' ]
     name: PHP ${{ matrix.php-versions }} Test on ${{ matrix.operating-system }} with WP ${{ matrix.wp }}
     steps:
     - name: Checkout