use unsigned mirror

Signed-off-by: Gregory Becker <becker33@llnl.gov>

Author: becker33

common/setup.rst

@@ -9,8 +9,7 @@
        git clone --depth=2 --branch=releases/v1.0 https://github.com/spack/spack
        . spack/share/spack/setup-env.sh
        spack repo update builtin --tag v2025.07.0
-       spack mirror add tutorial /mirror
-       spack buildcache keys --install --trust
+       spack mirror add --unsigned tutorial /mirror
        spack compiler find
 
    See the :ref:`basics-tutorial` for full details on setup. For more help, join us in the ``#tutorial`` channel on Slack -- get an invitation at `slack.spack.io <https://slack.spack.io/>`_