LineEdit undo behaves strangely

[mujpao]

Godot version:
4b6e9f3

OS/device including version:
Ubuntu 20.04.2 LTS

Issue description:
The undo operation on the LineEdit node behaves inconsistently and can sometimes undo text that was set from the "Text" property in the inspector, but only if you have made at least one change to the LineEdit since running the scene.

Steps to reproduce:
Open the minimal reproduction project.
Run the scene.
Select the LineEdit node, and try pressing undo. Nothing happens.
Try making a small change to the LineEdit text, and then undo that change. Undoing removes both the text you added and the initial text that was set from the inspector, all in one step.

On the other hand, selecting undo on the TextEdit node removes the initial text that was set from the inspector, even if you have not made any changes. This is probably how LineEdit should work?

Minimal reproduction project:
lineedit-undo-mrp.zip