gexp: Remove unused procedure.

* guix/gexp.scm (syntax-location-string): Remove.

guix/gexp.scm

@@ -1055,19 +1055,6 @@ and in the current monad setting (system type, etc.)"
                    reference->sexp (gexp-references exp))))
     (return (apply (gexp-proc exp) args))))
 
-(define (syntax-location-string s)
-  "Return a string representing the source code location of S."
-  (let ((props (syntax-source s)))
-    (if props
-        (let ((file   (assoc-ref props 'filename))
-              (line   (and=> (assoc-ref props 'line) 1+))
-              (column (assoc-ref props 'column)))
-          (if file
-              (simple-format #f "~a:~a:~a"
-                             file line column)
-              (simple-format #f "~a:~a" line column)))
-        "<unknown location>")))
-
 (define-syntax-rule (define-syntax-parameter-once name proc)
   ;; Like 'define-syntax-parameter' but ensure the top-level binding for NAME
   ;; does not get redefined.  This works around a race condition in a