This reverts commit 8cfa7f4d.

comment from sberg:
we already have 70519a43 "Replace OUStringBuffer::appendCopy with append(std::u16string_view)" (which can be extended to OStringBuffer if needed)

Change-Id: Ifcc550a8cf26ef38ad49fde8b067f53c999c9276
Reviewed-on: https://gerrit.libreoffice.org/70178
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>