Hide overwrites from disabled apps list on upgrade

If an incompatible app is enabled manually, it is added to the "app_install_overwrite" array in config.php. Nextcloud upgrades won't disable any app in this array, but they were still shown on the upgrade page as being disabled.

This commit assures that only apps are shown as "These incompatible apps will be disabled:" which are really disabled, i.e. which are not in the "app_install_overwrite" array.

Signed-off-by: MichaIng <micha@dietpi.com>