Previously it got a PROV_RSA_FULL provider, but SHA-256 needs
PROV_RSA_AES.

Change-Id: I6c689a4c5943920ce656c09d9d7d5e194ff47eb6
Reviewed-on: https://gerrit.libreoffice.org/22364Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>