fix unwanted deletion of attachments

[daiyam]

Description

This change fixes the unwanted deletions of attachments.

The issue is due to that a note can be changed between the editor has lost its focus and when the function removing unused attachments is run. The delay of 30s between the focus lost and cleanup was introduced for #3103.

How to reproduce the issue:

• click on the editor
• click on image you want to add to the note (the editor has lost its focus, the cleanup function will run in 30s)
• drag the image into the note but do not click in the editor
• wait 30s
• the image will have been deleted. (the image is still shown due to cache)

The fix: Every time that the note is changed, the call to the cleanup function is cancelled.

Issue fixed

• 3203

• 3424

Type of changes

• :radio_button: Bug fix (Change that fixed an issue)
• :white_circle: Breaking change (Change that can cause existing functionality to change)
• :white_circle: Improvement (Change that improves the code. Maybe performance or development improvement)
• :white_circle: Feature (Change that adds new functionality)
• :white_circle: Documentation change (Change that modifies documentation. Maybe typo fixes)

Checklist:

• :radio_button: My code follows the project code style
• :white_circle: I have written test for my code and it has been tested
• :radio_button: All existing tests have been passed
• :white_circle: I have attached a screenshot/video to visualize my change if possible
• :white_circle: This PR will modify the UI or affects the UX
• :white_circle: This PR will add/update/delete a keybinding

[daiyam]

@ZeroX-DG @Rokt33r I hope this fix can be included in the next version.