Disable test that uses bootstrap-guile.

Index: guix-debian/tests/gexp.scm
===================================================================
--- guix-debian.orig/tests/gexp.scm
+++ guix-debian/tests/gexp.scm
@@ -1193,6 +1193,7 @@ importing.* \\(guix config\\) from the h
       (return (and (zero? (close-pipe pipe))
                    (= (expt n 2) (string->number str)))))))
 
+(unless (network-reachable?) (test-skip 1))
 (test-assert "gexp->script #:module-path"
   (call-with-temporary-directory
    (lambda (directory)
