LibCore+Userland: Add DEPRECATED infix to REGISTER_STRING_PROPERTY macro

Author: https://github.com/krkk
Commit: ee5838084d
Pull-request: https://github.com/SerenityOS/serenity/pull/17800
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/awesomekling

Userland/Applications/SystemMonitor/main.cpp

@@ -97,7 +97,7 @@ public:
 private:
     UnavailableProcessWidget()
     {
-        REGISTER_STRING_PROPERTY("text", text, set_text);
+        REGISTER_DEPRECATED_STRING_PROPERTY("text", text, set_text);
     }
 
     virtual void paint_event(GUI::PaintEvent& event) override