nix: modules: knot: make git advertise push options

Signed-off-by: dusk <[e-mail]>

Change-Id: knxrqwrvtmylopmumymzxsqorunklwxz

nix/modules/knot.nix

···
         [user]
             name = Git User
             email = [e-mail]
+        [receive]
+            advertisePushOptions = true
         EOF
         chown -R ${cfg.gitUser}:${cfg.gitUser} "${cfg.stateDir}"
       '';