fix: use WordPress 6.8 in performance flow test

Latest Elementor from wordpress.org requires WordPress 6.8 minimum.
Update the Test Actions workflow to match.

Ref: ED-24451

Co-authored-by: Netanel Baba <Ntnelbaba@users.noreply.github.com>

Author: cursoragent

.github/workflows/test-actions.yml

@@ -20,7 +20,7 @@ jobs:
               uses: ./actions/setup-wp-env
               with:
                   php: '8.0'
-                  wp: '6.6'
+                  wp: '6.8'
                   active-theme: 'hello-elementor'
                   themes: |-
                       https://downloads.wordpress.org/theme/hello-elementor.zip