pull: Add missing import.

Fixes <https://bugs.gnu.org/34136>.
Reported by Pierre Neidhardt <mail@ambrevar.xyz>.

Fixes wrong-type-arg crash of "guix pull -p /does-not-exist -l".

* guix/scripts/pull.scm: Use (srfi srfi-34).

guix/scripts/pull.scm

@@ -46,6 +46,7 @@ (define-module (guix scripts pull)
   #:use-module ((gnu packages certs) #:select (le-certs))
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
   #:use-module (srfi srfi-37)
   #:use-module (ice-9 match)