notedeck : don't use an actual keystorage in Damus test apps

Reported-by: kernelkind

Fixes: https://github.com/damus-io/notedeck/issues/150

Signed-off-by: William Casarin

https://github.com/damus-io/notedeck/commit/5805df266a9701e40d291e10aa864ef65152e2fb