Editing is broken when being performed on a mobile device with the wiki editor and syntax highlighting

This might (or might not) be related to XWIKI-15553.

How to reproduce:

• Get a phone
• Go to a wiki running XWiki 10.7 with a browser
• Edit a page in wiki mode
• Try to remove a character (with the backspace key)

What happens is that the character gets removed, but a new line is also created just above the line that is being edited. If we try to remove this line, a new one is created and takes its place.

Tested on an LG v30 with Android 8.0.0 and the Firefox app, both the stock keyboard and the Swiftkey keyboard were used to perform the test.