Remove comment feature in "Dispute edit status" view in the tools' back office

[orlando]

In order to improve the user messaging flow, we will make some changes in the Dispute edit status view.

The idea is to keep admin communication inside the Back office, and move all the communication with the user to Discourse.

Tasks

• [x] Remove the comment box and the code related to it
• [x] Remove the Notify user checkbox and the code related to it
• [x] Add a link that opens in a new tab to the Dispute unique PM in Discourse

Acceptance criteria

• Comments UI was replaced with link to a Discourse PM
• Admin notes and the rest of the functionality works

[orlando]

After checking with @dawn3296, we want to keep this functionality, with #205 and #198 is enough.

Closing

[orlando]

Reopening this, we want to remove the comment box and change the notification message to just include something like

Your dispute status changed to {{status}}