fix: S2 MenuSection Typescript for children

[snowystinger]

Closes

Accidentally removed children as a function for the optional case when a header is not used

Introduced here: fc3ea3e#diff-9b1c24ddc8263e6dd0ff46a037608ba6678427cf11bd93ce7e1c034f7de2cdf3

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

## API Changes

@react-spectrum/s2

/@react-spectrum/s2:MenuSection

 MenuSection <T extends {}> {
   aria-label?: string
-  children?: ReactNode
+  children?: ReactNode | (T) => ReactElement
   defaultSelectedKeys?: 'all' | Iterable<Key>
   dependencies?: ReadonlyArray<any>
   disabledKeys?: Iterable<Key>
   disallowEmptySelection?: boolean
   items?: Iterable<T>
   onSelectionChange?: (Selection) => void
   selectedKeys?: 'all' | Iterable<Key>
   selectionMode?: SelectionMode
   shouldCloseOnSelect?: boolean
   value?: T
 }

/@react-spectrum/s2:MenuSectionProps

 MenuSectionProps <T extends {}> {
   aria-label?: string
-  children?: ReactNode
+  children?: ReactNode | (T) => ReactElement
   defaultSelectedKeys?: 'all' | Iterable<Key>
   dependencies?: ReadonlyArray<any>
   disabledKeys?: Iterable<Key>
   disallowEmptySelection?: boolean
   items?: Iterable<T>
   onSelectionChange?: (Selection) => void
   selectedKeys?: 'all' | Iterable<Key>
   selectionMode?: SelectionMode
   shouldCloseOnSelect?: boolean
   value?: T
 }

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