[simple-scan] Drop unused UI_DIR constant

[Robert Ancell <rancell src gnome org>]

commit 1c742dd8bdc1010a69308092d4dcdba11ee4506b
Author: Robert Ancell <robert ancell canonical com>
Date:   Tue Nov 13 12:12:46 2018 +1300

    Drop unused UI_DIR constant

 src/config.vapi | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/src/config.vapi b/src/config.vapi
index e6efeda..95a8497 100644
--- a/src/config.vapi
+++ b/src/config.vapi
@@ -3,5 +3,4 @@ public const string PKGDATADIR;
 public const string LOCALE_DIR;
 public const string GETTEXT_PACKAGE;
 public const string VERSION;
-public const string UI_DIR;
 public const string ICON_DIR;