fix: update non-focus-trap Popover role to be group

[smhigley]

Related to #21416

We do want to use a non-dialog role for the non-focus-trapping variant, but complementary isn't the best fit -- it refers specifically to content that is complementary to the main region, and on the same level as the main region in content hierarchy. That doesn't really apply to most popovers, so this PR updates it to the group role for the following reasons:

• Popovers may be nested, and group in particular enables that
• It's the lowest common accessible base role in that it is flexible in its use cases, and allows naming & exposes its bounds
• It is extremely flexible in allowed content (both in a strict spec sense, and in a general user expectation sense)

Other roles that were considered:

• note: it generally seems fine, but it would be weird to have nested notes, and it has a narrow range of expected use cases
• region: this would add popovers to the landmark list. It seems too heavy for something that is probably going to be a small, transient addition to the page, but we could reconsider it based on user feedback. The benefit would be that it would be easier to find with a screen reader's virtual cursor.

[fabricteam]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	188.672 kB 52.359 kB	188.664 kB 52.353 kB	-8 B -6 B
react-popover Popover	102.963 kB 31.553 kB	102.955 kB 31.548 kB	-8 B -5 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-alert Alert	83.511 kB 20.921 kB
react-avatar Avatar	48.381 kB 13.696 kB
react-avatar AvatarGroup	14.95 kB 5.989 kB
react-avatar AvatarGroupItem	68.349 kB 19.039 kB
react-components react-components: FluentProvider & webLightTheme	33.394 kB 11.007 kB
react-portal-compat PortalCompatProvider	5.851 kB 1.964 kB

_{🤖 This report was generated against 62aadfe9a8429fbc5c0660c1e741e5e8171f8f23}

[codesandbox-ci[bot]]

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@fluentui/react 8 starter	Configuration
@fluentui/react-components 9 starter	Configuration

[size-auditor[bot]]

Asset size changes

Size Auditor did not detect a change in bundle size for any component!

Baseline commit: 62aadfe9a8429fbc5c0660c1e741e5e8171f8f23 (build)

[fabricteam]

Perf Analysis (@fluentui/react-components)

No significant results to display.

All results

Scenario	Render type	Master Ticks	PR Ticks	Iterations	Status
Avatar	mount	1584	1618	5000
Button	mount	1179	1144	5000
FluentProvider	mount	1912	1930	5000
FluentProviderWithTheme	mount	767	760	10
FluentProviderWithTheme	virtual-rerender	715	732	10
FluentProviderWithTheme	virtual-rerender-with-unmount	766	769	10
MakeStyles	mount	2323	2344	50000
SpinButton	mount	3184	3085	5000