home: services: Add missing import.

* gnu/home/services.scm: Import (srfi srfi-34) for ‘raise’.

Change-Id: Ib0e8d134f3953c78a09b623f697e7e5b251d5611

gnu/home/services.scm

@@ -37,6 +37,7 @@
   #:use-module (guix memoization)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-34)
   #:use-module (ice-9 match)
   #:use-module (ice-9 vlist)