gui: bump theme version to 2

Commit 9472ba1d introduced new behavior for KEY_POWER which
needs a corresponding change in the theme to call the
setbacklight action whenever the power button is pressed.

Change-Id: Iacd46436b04aba1ecb1adbb684c56c3ef994bfe0
diff --git a/gui/pages.cpp b/gui/pages.cpp
index 5c647c3..b2a978f 100644
--- a/gui/pages.cpp
+++ b/gui/pages.cpp
@@ -51,7 +51,9 @@
 #include "objects.hpp"
 #include "blanktimer.hpp"
 
-#define TW_THEME_VERSION 1
+// version 2 requires theme to handle power button as action togglebacklight
+#define TW_THEME_VERSION 2
+
 #define TW_THEME_VER_ERR -2
 
 extern int gGuiRunning;