Y-size of GraphNodes with RichTextLabel and "Fit Content: True" gets huge when reloading scene

### Tested versions

Tested on v4.2.1.stable.mono.official [b09f793f5]
NOTE: No scripting is necessary, so mono/non-mono should not matter (in theory).

### System information

Godot v4.2.1.stable.mono - EndeavourOS #1 SMP PREEMPT_DYNAMIC Thu, 11 Apr 2024 01:47:33 +0000 - Wayland - Vulkan (Forward+) - dedicated AMD Radeon RX 7800 XT (RADV NAVI32) () - AMD Ryzen 5 3600 6-Core Processor (12 Threads)

### Issue description

Title, basically. When a `GraphNode` contains a `RichTextLabel` with "Fit Content" set to true, reloading the scene will cause the graph node to expand along the Y axis to a ridiculous degree. The issue seems related to the size of the `GraphEdit`, a larger graph will result in larger Y-size.

### Steps to reproduce

1. Add a `GraphEdit` with one or more `GraphNode`s as children
2. Add a `RichTextLabel` with some text as a child of one of the `GraphNode`s
3. Check the "Fit Content" option
4. Reload the scene
5. The nodes containing the rich text are now huge.

### Minimal reproduction project (MRP)

[graph-edit-rich-text-bug-demo.zip](https://github.com/godotengine/godot/files/15023398/graph-edit-rich-text-bug-demo.zip)

No scripts are used, should be independent of C#/GDscript

Open the linked graph-edit-rich-text-bug-demo.zip and reproduce the issue with GraphEdit, GraphNode, and RichTextLabel using Fit Content. Trace the layout and sizing behavior during scene reload, especially how GraphEdit size affects the node's Y dimension. Done means reloading the scene no longer makes nodes containing fitted RichTextLabels grow to an excessive height.

Written by the indexing model from the issue text.