Odd wrapping behavior of the bottom toolbar in the Animation dock when shrinking it horizontally

### Tested versions

- Reproducible in v4.8.dev.custom_build [4e8c061c9]

### System information

Godot v4.8.dev (4e8c061c9) - Windows 10 (build 19045) - Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3050 Ti Laptop GPU (NVIDIA; 32.0.16.1074) - AMD Ryzen 5 5600H with Radeon Graphics (12 threads) - 15.34 GiB memory - WASAPI (48000 Hz, Stereo/mono)

### Issue description

When adjusting the width of different docks and shrinking the bottom dock, the Animation's dock "fit to panel" control gets carried over onto the next line.

Although visually there is enough space for it and it breaks the visual grouping of the zoom controls.

### Steps to reproduce

Shrink the Animation dock.

### Minimal reproduction project (MRP)

N/A

No source file or test is named. Start by reproducing the issue in the Animation dock while shrinking the bottom dock, then trace the Animation dock UI entry point responsible for the toolbar layout. Done means the fit-to-panel control remains grouped with the zoom controls when the dock is narrowed, without introducing regressions at other widths.

Written by the indexing model from the issue text.