Fix Label autowrap clips text

[volzhs]

This PR prevent to clip text when using only Autowrap

but it shows over than its size when can't wrap.

if really want, Clip text can be used together.

Fix #20226

[volzhs]

we have Rect > Clip Content for all Control nodes now.
so, Label.clip_text is actually not needed anymore.
but it breaks compatibility so... maybe later...

[akien-mga]

Now that Godot 3.1 has been released, we only plan to cherry-pick critical bug fixes to the 3.0 branch, unless there is very strong support in favor of a specific non-critical issue. Removing cherrypick label for 3.0.

[AaronRecord]

clip_content doesn't seem to currently work for buttons or labels.