Rename package to xfce4

pkg.info

@@ -1,8 +1,8 @@
-name: xfce
+name: xfce4
 description: The Xfce Desktop Environment
-version: 4.18
-revision: 2
+version: 4.20
 url: https://www.xfce.org/
 architecture: any
 depends: ["exo","garcon","thunar","thunar-volman","tumbler","xfce4-appfinder","xfce4-panel","xfce4-power-manager","xfce4-session","xfce4-settings","xfconf","xfdesktop","xfwm4"]
+replaces: ["xfce"]
 type: source