Apply suggestions from code review

Co-authored-by: Norman Ziegner <normo157@gmail.com>

Author: tobiashuste

roles/gitlab/README.md

@@ -397,7 +397,8 @@ gitlab_postgresql_db_password: 'changeme'
 Configure the monitoring whitelist for GitLab-Rails:
 
 ```yaml
-gitlab_rails_monitoring_whitelist: ["{{ gitlab_ip_range }}"]
+gitlab_rails_monitoring_whitelist:
+  - "{{ gitlab_ip_range }}"
 ```
 
 #### Configure GitLab Registry

roles/gitlab/defaults/main.yml

@@ -95,8 +95,9 @@ gitlab_mattermost_only_context: "false"
 
 gitlab_feature_flags: []
 
-gitlab_rails_monitoring_whitelist: ["{{ gitlab_ip_range }}"]
-
+# List of IP addresses or IP ranges that are allowed to access monitoring endpoints
+gitlab_rails_monitoring_whitelist:
+  - "{{ gitlab_ip_range }}"
 # Internal variable to determine whether the configuration object for Gitaly
 # is already present in gitlab_additional_configurations
 __gitaly_configuration_exists: false