[gnome-builder] Update POTFILES.in

[Piotr Drąg <piotrdrag src gnome org>]

commit 7f6a4b7a781099369cf4c4202fdd266c6f136621
Author: Piotr Drąg <piotrdrag gmail com>
Date:   Wed Mar 28 00:40:44 2018 +0200

    Update POTFILES.in

 po/POTFILES.in | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 7244d54a1..d9f886582 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -217,6 +217,7 @@ src/plugins/spellcheck/gbp-spell-widget.ui
 src/plugins/spellcheck/gtk/menus.ui
 src/plugins/support/gtk/menus.ui
 src/plugins/support/ide-support-application-addin.c
+src/plugins/symbol-tree/gbp-symbol-layout-stack-addin.c
 src/plugins/symbol-tree/gbp-symbol-menu-button.c
 src/plugins/symbol-tree/gbp-symbol-menu-button.ui
 src/plugins/sysmon/gb-sysmon-panel.ui