Fix `line_spacing` in code editor will not take effect immediately on change

Previously, in CodeTextEditor, `line_spacing` was forgotten to update
when the editor setting property changed.

(cherry picked from commit 23d6225c1e59f33cc6cfe0df3a00961c0c93155f)

editor/code_editor.cpp

@@ -1047,6 +1047,7 @@ void CodeTextEditor::update_editor_settings() {
 	// Appearance: Whitespace
 	text_editor->set_draw_tabs(EDITOR_GET("text_editor/appearance/whitespace/draw_tabs"));
 	text_editor->set_draw_spaces(EDITOR_GET("text_editor/appearance/whitespace/draw_spaces"));
+	text_editor->add_theme_constant_override("line_spacing", EDITOR_GET("text_editor/appearance/whitespace/line_spacing"));
 
 	// Behavior: Navigation
 	text_editor->set_scroll_past_end_of_file_enabled(EDITOR_GET("text_editor/behavior/navigation/scroll_past_end_of_file"));