Inspector theme doesn't update between light and dark theme until another node is selected

[Calinou]

Godot version

4.1.1.stable, 4.2.dev 541674d

System information

Godot v4.2.dev (541674d) - Fedora Linux 38 (KDE Plasma) - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 535.98) - 13th Gen Intel(R) Core(TM) i9-13900K (32 Threads)

Issue description

The inspector theme doesn't update between light and dark theme until another node is selected:

For example, after switching from light to dark theme, you initially see this in the inspector:

If you switch to another node in the inspector (or deselect all nodes then select a node again), section and icon colors will appear correctly (i.e. with darker tones).

Steps to reproduce

• Select a node in the Scene tree dock.
• Set the editor theme to Light in the Editor Settings.
• Notice the sections' and icons' color in the inspector.
• Select another node (or deselect all nodes then select a node again).
• Notice how the theme now appears correctly.

Minimal reproduction project

N/A

[YuriSizov]

This is a duplicate of #70356. I plan to look into it at some point, it just needs a bit of theme changed notification handling, but it's not so trivial (see #70381).