Revert "gnutls: Change the GnuTLS priority string from NORMAL to SECURE256"
Revert "gnutls: Change the GnuTLS priority string from NORMAL to SECURE256"

On gnutls 2.12.x, SECURE256 just changes the preferred negotiation
order, but on 3.0.x, it means "disable all non-256-bit ciphers", which
breaks many sites.

This reverts commit 6550c7e9cf928b13ed1d1167004c1f6e16e0173f.

GNOME/glib-networking,Distrotech/glib-networking,GNOME/glib-networking,GNOME/glib-networking,Distrotech/glib-networking,Distrotech/glib-networking