self: Remove unused variable.

This variable is unused since commit
45779fa6.

* guix/self.scm (%dependency-variables): Remove.
* build-aux/build-self.scm (%dependency-variables): Remove.

build-aux/build-self.scm

@@ -54,10 +54,6 @@ (define-module (build-self)
 ;;; available at this point.
 ;;;
 
-(define %dependency-variables
-  ;; (guix config) variables corresponding to dependencies.
-  '(%libgcrypt %libz %xz %gzip %bzip2))
-
 (define %persona-variables
   ;; (guix config) variables that define Guix's persona.
   '(%guix-package-name

guix/self.scm

@@ -753,10 +753,6 @@ (define (built-modules node-subset)
 ;;; Generating (guix config).
 ;;;
 
-(define %dependency-variables
-  ;; (guix config) variables corresponding to dependencies.
-  '(%libz %xz %gzip %bzip2))
-
 (define %persona-variables
   ;; (guix config) variables that define Guix's persona.
   '(%guix-package-name