Foldout elements in UI documents create an invisible focusable element when the "Focusable" field is enabled

How to reproduce:
1. Open the attached "foldout_issue" project
2. Open the "SampleScene" and enter Play mode
3. Select one of the buttons in the Game view to focus on it
4. Navigate through the different elements with the Tab and Shift+Tab keys
5. Observe the result

Expected result: When navigating from the last radio button to the Foldout element, only a single press of the Tab key is required
Actual result: Navigating from the last radio button to the Foldout element requires two keyboard presses due to an invisible element

Reproducible in: 2021.3.37f1, 2022.3.23f1, 2023.2.17f1, 6000.0.0b14

Reproducible on: Windows 11
Not reproducible on: No other environments tested

Note: Reproducible in Player