offload: Fix error message in 'guix offload test'.

Reported by Maxim Cournoyer <maxim.cournoyer@gmail.com>
in <https://bugs.gnu.org/31824>.

* guix/scripts/offload.scm (assert-node-has-guix): Fix typo in failure
message; add missing argument.

guix/scripts/offload.scm

@@ -613,8 +613,8 @@ If TIMEOUT is #f, simply evaluate EXP..."
          (leave (G_ "failed to talk to guix-daemon on '~a' (test returned ~s)~%")
                 name x))))
     (lambda (key . args)
-      (leave (G_ "remove evaluation on '~a' failed:~{ ~s~}~%")
-             args))))
+      (leave (G_ "remote evaluation on '~a' failed:~{ ~s~}~%")
+             name args))))
 
 (define %random-state
   (delay