fix #43695 by revert part of #41576

Note that #42109 already reverted the change of MenuButton,
and actually fixed #43695.
As a result, this commit only reverts the change to LinkButton,
in order to prevent unpredictable consequences.

scene/gui/link_button.cpp

@@ -295,5 +295,6 @@ void LinkButton::_bind_methods() {
 LinkButton::LinkButton() {
 	text_buf.instance();
 	underline_mode = UNDERLINE_MODE_ALWAYS;
+	set_focus_mode(FOCUS_NONE);
 	set_default_cursor_shape(CURSOR_POINTING_HAND);
 }