Extra lines currently render empty list items which are invisible.
Remove these as the user probably didn't intend from them to appear
in the wikiext.
Bug: T249867
Change-Id: I75c1192a94b918783d362d38cd91a508bb169d56
3 or 5 tilde signatures will be assumed to be erroneous and fixed
to 4 tilde signatures. This will be visible in the preview so shouldn't
come as a suprise to users.
Bug: T245628
Change-Id: I741f0761a6fb10c99cf3239ac5c6c7e1a2b872c7