Add option to uninstall TWRP app from /system

Change-Id: Ibe372a372333c357810be2afcb3796723ca370cb
diff --git a/gui/objects.hpp b/gui/objects.hpp
index 2e306e0..3f72418 100644
--- a/gui/objects.hpp
+++ b/gui/objects.hpp
@@ -367,6 +367,7 @@
 	int twcmd(std::string arg);
 	int setbootslot(std::string arg);
 	int installapp(std::string arg);
+	int uninstalltwrpsystemapp(std::string arg);
 	int repackimage(std::string arg);
 	int fixabrecoverybootloop(std::string arg);