upgrade to ICU 52.1, fdo#70995

Change-Id: I25e4b630c9029749cc459c0b65da287d6f0ba95e
Reviewed-on: https://gerrit.libreoffice.org/6666
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>