Drop deprecated Prometheus settings in gitlab.yml

Remove support for prometheus.listen_address and prometheus.enable in gitlab.yml

Changelog: removed

config/initializers/1_settings.rb

@@ -917,13 +917,8 @@ Settings.monitoring.web_exporter['port'] ||= 8083
 # Prometheus settings
 #
 Settings['prometheus'] ||= Settingslogic.new({})
-# TODO: Remove listen_address and enable in GitLab 14.0 and set default value
-# of server_address to be nil and enabled to be false -
-# https://gitlab.com/gitlab-org/gitlab/-/issues/296022
-Settings.prometheus['enable'] ||= false
-Settings.prometheus['listen_address'] ||= nil
-Settings.prometheus['enabled'] = Settings.prometheus['enable'] if Settings.prometheus['enabled'].nil?
-Settings.prometheus['server_address'] ||= Settings.prometheus['listen_address']
+Settings.prometheus['enabled'] ||= false
+Settings.prometheus['server_address'] ||= nil
 
 #
 # Shutdown settings