SegmentedButton - sx props do not apply

[lesliecdubs]

Describe the bug
As originally reported in #2267:

I'd like to be able to specify the SegmentedControl.Button as a small size as I can with other buttons
size is not a supported prop of SegmentedControl.Button - so I tried setting the fontSize through sx prop and it still has no effect.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://primer.style/react/SegmentedControl
2. Note that size is not a supported prop for the Button
3. Add sx={{fontSize: 0}} to one of the buttons
4. Notice that nothing changes

Expected behavior
sx prop should apply to SegmentedControl.Button.

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS] MacOS
• Browser [e.g. chrome, safari] Chrome
• Version [e.g. 22] 104

[mperrotti]

Planning to work on this bug this week.

[lesliecdubs]

Thanks for the update @mperrotti! I moved this into "Up Next: Design" on the Primer teams backlog to match the status. I'd definitely focus on #2267 first, unless you'd rather the team handle this new size through the sx prop in the longer term.

[mperrotti]

@lesliecdubs - I'd rather the team use the size prop. A PR has been merged to support the size prop: #2347