#17284 Edit form does not cancel correctly

## What does this MR do?

Replaces the markdown textarea with the currently saved note text when the note edit is cancelled.

## Are there points in the code the reviewer needs to double check?

No

## Why was this MR needed?

Allows the user to revert back to the original note text, as expected, using cancel.

## What are the relevant issue numbers?

Fixes #17284.

## Screenshots

![17284](/uploads/c3598de6f8e70d52275ef25907d92d42/17284.gif)

See merge request !4175