zabbix: tweak frontend dependencies

zabbix: tweak frontend dependencies

For zabbix-server-frontend, the absence of php8-mod-filter results in
many of the frontend's pages failing to render.  Therefore add this
module as a frontend dependency.

Without php8-mod-openssl the frontend fails with:

[13-Dec-2025 18:47:25 UTC] PHP Fatal error:  Uncaught Error: Call to
undefined function openssl_random_pseudo_bytes() in
/www/zabbix/include/classes/helpers/CEncryptHelper.php:89
Stack trace:
CEncryptHelper::generateKey()
  thrown in /www/zabbix/include/classes/helpers/CEncryptHelper.php on
  line 89

Therefore add php8-mod-openssl as a frontend dependency.

Signed-off-by: Daniel F. Dickinson <dfdpublic@wildtechgarden.ca>