Enable deleting annotations in the edit box of the coding interface

[tanius]

Issue demonstration:

1. Go to any Discourse topic and click on "Code with Open Ethnographer" to go to the coding interface.

2. Select some text, open the coding popover window, add at least one code, and save.

3. Hover over the text that you previously selected, and click the pen button for one of the annotations you created, to edit it.

4. Click the "×" or use the backspace key to remove the code from the edit box.

5. Click "Save".

Now the issue is that this "Save" action (basically deleting the annotation) is not executed. Instead, a message appears "Sorry something went wrong with the annotation store".