docs: remove GnuPG limitation of repo verification

We also support to verify repos using SSH keys from the first version
on. This limitation was forgotten to be removed during reworking the
patch series.

Fixes: 8051eaa ("extend kas schema to provide repo signing ...")
Signed-off-by: Felix Moessbauer <[email protected]>
Signed-off-by: Jan Kiszka <[email protected]>

Author: fmoessbauer

docs/userguide/project-configuration.rst

@@ -467,8 +467,6 @@ Configuration reference
   available to the build environment as well by pointing the ``GNUPGHOME``
   environment variable to the local keystore.
 
-  .. note:: Currently only GnuPG keys are supported.
-
   ``<signer_id>``: dict [optional]
     :kasschemadesc:`signers.additionalProperties`
     For each signer, a unique identifier is required. The ``<signer_id>`` is used to