feat: move deps to playbook

Remove galaxy dependencies from role meta and add explicit
include_role tasks in the playbook instead.

meta/main.yaml

@@ -5,7 +5,4 @@ galaxy_info:
   description: "install and configure a Zabbix Web server"
   license: "MIT"
   role_name: "zabbix_web"
-dependencies:
-  - name: "zabbix_prereq"
-    src: "git+https://gitlab.simoncor.net/ansible/ans-zabbix-prereq.git"
-    version: "main"
+dependencies: []