[gimp] app: reorder alphabetically file list in meson build.

[Jehan <jehanp src gnome org>]

commit c033b3498f7a7115d78d7928a7d3bd34a4caf197
Author: Jehan <jehan girinstud io>
Date:   Mon Nov 4 14:48:52 2019 +0100

    app: reorder alphabetically file list in meson build.
    
    Just fixing previous commit like this instead of wasting time in gitlab
    with useless reviews for oneliners. When will gitlab allow us to amend
    patches directly before merge?!

 app/core/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/core/meson.build b/app/core/meson.build
index 0392bb9d33..ebfecf3812 100644
--- a/app/core/meson.build
+++ b/app/core/meson.build
@@ -168,8 +168,8 @@ libappcore_sources = [
   'gimpimage-undo.c',
   'gimpimage.c',
   'gimpimagefile.c',
-  'gimpimageundo.c',
   'gimpimageproxy.c',
+  'gimpimageundo.c',
   'gimpitem-exclusive.c',
   'gimpitem-linked.c',
   'gimpitem-preview.c',