gnu: glade: Update to 3.20.0.

* gnu/packages/gnome.scm (glade): Update to 3.20.0.

gnu/packages/gnome.scm

@@ -760,7 +760,7 @@ (define-public gtkglext
 (define-public glade3
   (package
     (name "glade")
-    (version "3.18.3")
+    (version "3.20.0")
     (source (origin
               (method url-fetch)
               (uri (string-append "mirror://gnome/sources/" name "/"
@@ -768,7 +768,7 @@ (define-public glade3
                                   name "-" version ".tar.xz"))
               (sha256
                (base32
-                "0lk4nvd5s8px9i0pbq7bncikgn2lpx7vjh787d3cvzpvwx3cxnzc"))))
+                "1zhqvhagy0m85p54jfiayfl0v9af7g0lj7glw8sfwh7cbp56vnc2"))))
     (build-system gnu-build-system)
     (arguments
      `(#:tests? #f ; needs X, GL, and software rendering