Annotated words that were modified are not differentiated anymore

Steps to reproduce

1. Go to a page with text content (e.g. Sandbox)
2. Select a word
3. Press CTRL+M, add some annotation text
4. Click 'Add annotation'
5. Observe the color of the highlighted (annotated) word
6. Edit the page and modify the annotated word (add/remove some letters)
7. Save the page
8. Enable annotations display and observe again the color of the highlighted (modified) word

Expected results

The highlight color of the modified word is different than the color of an un-modified word, to let the users know that there was a modification that needs to be reviewed.

Actual results

The highlight color of both modified and un-modified words is the same, therefore the users need to check all annotations on the page to see if a review is needed.

The issue was not present in XWiki 17.10.x, the color of the icon for an un-modified word was yellow and the icon's color for a modified word was orange (see the screenshot).