GnuTLS 3.5 is now the supported stable version of GnuTLS.
As a security-critical component, it should be kept updated.
GnuTLS 3.5 requires Nettle 3.3, also bumped.

GnuTLS 3.5.11 adds support for the macOS system key chain,
so the related patch is removed.

Change-Id: Ie5eb54e195083dadedde7daabf227f77cca7105e
Reviewed-by: Olivier Soldano <olivier.soldano@savoirfairelinux.com>