Remove Disabled option from Progress calculation setting

Also renamed the other options to Work-based and Status-based, and added
an explanation of the two options.

app/models/work_package.rb

@@ -43,7 +43,7 @@ class WorkPackage < ApplicationRecord
 
   include OpenProject::Journal::AttachmentHelper
 
-  DONE_RATIO_OPTIONS = %w(field status disabled).freeze
+  DONE_RATIO_OPTIONS = %w[field status].freeze
 
   belongs_to :project
   belongs_to :type

app/views/admin/settings/work_packages_settings/show.html.erb

@@ -36,7 +36,12 @@ See COPYRIGHT and LICENSE files for more details.
     <div class="form--field"><%= setting_check_box :cross_project_work_package_relations %></div>
     <div class="form--field"><%= setting_check_box :display_subprojects_work_packages %></div>
     <div class="form--field"><%= setting_check_box :work_package_startdate_is_adddate %></div>
-    <div class="form--field"><%= setting_select :work_package_done_ratio, WorkPackage::DONE_RATIO_OPTIONS.collect { |i| [t("setting_work_package_done_ratio_#{i}"), i] }, container_class: "-middle" %></div>
+    <div class="form--field">
+      <%= setting_select :work_package_done_ratio,
+                         WorkPackage::DONE_RATIO_OPTIONS.collect { |i| [t("setting_work_package_done_ratio_#{i}"), i] },
+                         container_class: "-middle" %>
+      <div class="form--field-instructions"><%= t("setting_work_package_done_ratio_explanation_html") %></div>
+    </div>
     <div class="form--field settings--highlighting-mode">
       <%= setting_select(:work_package_list_default_highlighting_mode,
                          Query::Highlighting::QUERY_HIGHLIGHTING_MODES.map do |mode|

config/locales/en.yml

@@ -3019,10 +3019,12 @@ Project attributes and sections are defined in the <a href=%{admin_settings_url}
   setting_file_max_size_displayed: "Max size of text files displayed inline"
   setting_host_name: "Host name"
   setting_invitation_expiration_days: "Activation email expires after"
-  setting_work_package_done_ratio: "Calculate work package % Complete with"
-  setting_work_package_done_ratio_field: "The work package field"
-  setting_work_package_done_ratio_status: "The work package status"
-  setting_work_package_done_ratio_disabled: "Disable (hide the % Complete field)"
+  setting_work_package_done_ratio: "Progress calculation"
+  setting_work_package_done_ratio_field: "Work-based"
+  setting_work_package_done_ratio_status: "Status-based"
+  setting_work_package_done_ratio_explanation_html: >
+    In work-based mode, % Complete is calculated from how much work is done in relation to total work.<br>
+    In status-based mode, each status has a % Complete value associated with it. Changing status will change % Complete.
   setting_work_package_properties: "Work package properties"
   setting_work_package_startdate_is_adddate: "Use current date as start date for new work packages"
   setting_work_packages_projects_export_limit: "Work packages / Projects export limit"