Can't shrink label past former maximum text size

[KoBeWi]

Godot version

953de68

System information

W10

Issue description

Looks like variation of #40357. When you select text and delete all of it at once, the minimum size doesn't get updated properly.

Works fine if I backspace it char by char.

Steps to reproduce

1. Create Label
2. Add some text that will make it bigger
3. Select the text and press Backspace to delete all at once
4. Try shrinking Label

Minimal reproduction project

No response