deleting a label

[jpcbertoldo]

(i'm not sure if this is intended) deleting a label in the config creates a weird state where the previous annotations still exist with the deleted label, but the menu of labels doesnt show it

i see two possible solutions (not exclusive btw) to improve this:

• before deleting a label, warn the user of what will happen
• put a warning sign in the annotations to let the user know it should be changed

ubuntu 20.04, chrome 130

I wrote this is part of my review to JOSS openjournals/joss-reviews#7210