applets/notes: make default paste action enable clickable URLs by default

Currently, when pasting text into the Notes widget, formatting is removed, and as a result URLs are not clickable. When using notes to store a link for later usage, this always requires the user to manually select the link text and copy and paste it into a browser, which is annoying. This commit solves that issue by making the default paste action only strip non-link formatting; links remain formatted and hence clickable.