utils: 'wrap-script' doesn't pass a non-literal string to 'format'.

Reported by Vagrant Cascadian <vagrant@debian.org>
in <https://bugs.gnu.org/44626>.

* guix/build/utils.scm (wrap-script): Use 'display' instead of passing a
non-literal string to 'format'.

guix/build/utils.scm

@@ -1347,7 +1347,7 @@ not supported."
                 (lambda ()
                   (call-with-ascii-input-file prog
                     (lambda (p)
-                      (format out header)
+                      (display header out)
                       (dump-port p out)
                       (close out)
                       (chmod template mode)