guix package: '-s' displays different packages that have the same location.

Before that, 'guix package -s foobarbaz' would display only one package
when several match but they have the same location (which is common when
using 'inherit'.)

The original rationale was given at
<http://lists.gnu.org/archive/html/bug-guix/2013-01/msg00280.html> but
it was arguably misguided because it led to "real" packages being
hidden.

Reported by Tomáš Čech <sleep_walker@gnu.org>.

* guix/scripts/package.scm (find-packages-by-description)[same-location?]:
  Remove.
  Remove call to 'delete-duplicates'.

guix/scripts/package.scm

@@ -240,11 +240,6 @@ DURATION-RELATION with the current time."
 (define (find-packages-by-description rx)
   "Return the list of packages whose name, synopsis, or description matches
 RX."
-  (define (same-location? p1 p2)
-    ;; Compare locations of two packages.
-    (equal? (package-location p1) (package-location p2)))
-
-  (delete-duplicates
   (sort
    (fold-packages (lambda (package result)
                     (define matches?
@@ -260,8 +255,7 @@ RX."
                   '())
    (lambda (p1 p2)
      (string<? (package-name p1)
-                (package-name p2))))
-   same-location?))
+               (package-name p2)))))
 
 (define-syntax-rule (leave-on-EPIPE exp ...)
   "Run EXP... in a context when EPIPE errors are caught and lead to 'exit'