DEV: Promote historic post_deploy migrations

This commit promotes all post_deploy migrations which existed in Discourse v2.6.7 (timestamp <= 20201110110952)

db/migrate/20200724060632_remove_deprecated_allowlist_settings.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class RemoveDeprecatedAllowlistSettings < ActiveRecord::Migration[6.0]
+  def up
+    SiteSetting::ALLOWLIST_DEPRECATED_SITE_SETTINGS.each_pair do |old_key, _new_key|
+      DB.exec <<~SQL
+        DELETE FROM site_settings
+        WHERE name = '#{old_key}'
+      SQL
+    end
+  end
+
+  def down
+    SiteSetting::ALLOWLIST_DEPRECATED_SITE_SETTINGS.each_pair do |old_key, new_key|
+      DB.exec <<~SQL
+        INSERT INTO site_settings(name, data_type, value, created_at, updated_at)
+        SELECT '#{old_key}', data_type, value, created_at, updated_At
+        FROM site_settings
+        WHERE name = '#{new_key}'
+      SQL
+    end
+  end
+end