Don't have the inclusion of lang_enum.h depend on PLUGIN

This #ifdef apparcntly confuses dependency generation, and since lang_enum.h
just declares an enum, including it unconditionally is harmless.

Change-Id: I8feaff7657080962f1ae6305492075c8a5bca673
diff --git a/apps/plugin.h b/apps/plugin.h
index 083dac0..a83960b 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -71,9 +71,7 @@
 #include "mp3_playback.h"
 #include "root_menu.h"
 #include "talk.h"
-#ifdef PLUGIN
 #include "lang_enum.h"
-#endif
 #ifdef RB_PROFILE
 #include "profile.h"
 #endif