Upgrade WordPress Docker image to v6.8.0

[stephdl]

Brief description
We request to update the WordPress Docker image from its current version to v6.8.0.
WHY: The newer version includes critical security patches, performance improvements, and enhanced compatibility with themes and plugins.

PURPOSE: Ensure our WordPress deployments benefit from upstream fixes, maintain plugin compatibility, and stay aligned with best practices for containerized applications.

Proposed solution

Update the WordPress Docker image tag to v6.8.0

Alternative solutions
Staying on the current version is discouraged as it increases exposure to known vulnerabilities and risks plugin/theme incompatibility. Selective patching is not feasible with container-based images.

[stephdl]

QA

target version is ghcr.io/nethserver/wordpress:1.0.9-dev.1

• direct install, no issue expected
• upgrade
  install ghcr.io/nethserver/wordpress:1.0.8
  configure it
  upgrade to ghcr.io/nethserver/wordpress:1.0.9-dev.1
  the upgrade even done from the nethserver package, you have to use the installer from the wordpress UI
  Do all the upgrade from the wordpress UI, no issue expected

[stephdl]

community verification asked at https://community.nethserver.org/t/wordpress-6-8-needs-testers/25746

[mrmarkuz]

Direct install and update verified

• Upgrades of app, plugins and themes in Wordpress UI worked