Remove checks for HTMLMODE_SOME_STYLES

HTMLMODE_SOME_STYLES is enabled for all supported HTML export
modes so there is never need to disable these elements in
the paragraph dialog.

Change-Id: I43df54a6ce900c8a9f957522eb85ca67b6cd756f
Reviewed-on: https://gerrit.libreoffice.org/12091
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>