CodeEditor: Drop unused enable_complete_timer variable

Its use was removed in 1039ba9ffb8588e8b0abddaa753d270979147c23.

editor/code_editor.h

@@ -152,7 +152,6 @@ class CodeTextEditor : public VBoxContainer {
 	Label *info;
 	Timer *idle;
 	Timer *code_complete_timer;
-	bool enable_complete_timer;
 
 	Timer *font_resize_timer;
 	int font_resize_val;