The underlying issue was fixed by Miklos in commit
9d754a59 ("sw: give
the 'Default Style' char style a programmatic name").
What left is to actually use the internal name in
various UI elements.

Also removed a comment that tells to not rename the
default style, which isn't relevant anymore, as we
no longer write the UI name into files.

Change-Id: Ie2ab632e40b4fc6295f2c9d1a1f1f2358ab38e52
Reviewed-on: https://gerrit.libreoffice.org/58311
Tested-by: Jenkins
Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>