Font Size Picker: Remove Custom option from FontSizePickerSelect dropdown

[himanshupathak95]

What?

Closes #69029

Removes the 'Custom' option from the FontSizePicker's select dropdown while maintaining custom font size functionality through the settings icon button.

Why?

The current implementation includes a 'Custom' option in the font size dropdown when there are more than 5 font sizes. This creates two issues:

• Semantically incorrect: A select/listbox control should contain values, not interactive controls that change the UI
• Accessibility violation: When using keyboard navigation, reaching the 'Custom' option unexpectedly changes the entire UI context and loses focus
• Redundant functionality: The same custom size feature is already available through the settings icon button

Testing Instructions

• Use a theme with more than 5 font sizes (e.g., modify Twenty Twenty-Four's theme.json to add extra font sizes)
• Open the block editor
• Select a Paragraph block
• Click on the Font size picker in the inspector panel and verify the "Custom" option is removed

Testing Instructions for Keyboard

• Use a theme with more than 5 font sizes (e.g., modify Twenty Twenty-Four's theme.json to add extra font sizes)
• Open the block editor
• Use Tab to focus on the font size and select dropdown
• Use arrow keys to navigate through options
• Verify that no unexpected UI changes occur

Screencast

Before -

Screen.Recording.2025-02-05.at.10.45.04.mov

After -

Screen.Recording.2025-02-05.at.10.32.17.mov

[himanshupathak95]

This PR currently just removes the "Custom" option from the dropdown for the reasons mentioned by @afercia in #69029 (comment)

This is a WIP and the following things can be implemented after discussion -

• Opening of the dropdown and persistence while navigating options through keystrokes
• Autofocus on the custom sizes control

This is a screencast of the current changes -

Before -

Screen.Recording.2025-02-05.at.10.45.04.mov

After -

Screen.Recording.2025-02-05.at.10.32.17.mov

After discussing and refining the approach, I will take care of the failing test cases.

[afercia]

@himanshupathak95 thanks for the PR.
I'd suggest to keep the changes into the scope of the issue and not proceed with the additional points.
When you have a chance, please add the What, Why, How, Testing Instructions to the PR description so it can be reviewed 🙏🏻

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[himanshupathak95]

Thanks for the suggestions @afercia 🙌🏻

I have removed the unit tests that accounted for the "Custom" option, and I have also updated the PR description. Please take a look whenever time permits and let me know if it tests well for you 🙇🏻

[afercia]

Thanks for working on this @himanshupathak95
Looks good to me. The only thing left is adding a changelog entry in packages/components/CHANGELOG.md

[afercia]

LGTM