docs: fix typos in documentation

[olitreadwell]

Closes

✅ 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
• I understand every change in this PR and can explain why it's there.

📝 Test Instructions:

Docs-only cleanup: 13 typo fixes across 10 files (CONTRIBUTING.md, React Spectrum release notes, s2-docs pages, and an RFC). No code or behavior changes, so no unit tests are required.

🧢 Your Project:

Open-source contribution.

How to verify

git fetch https://github.com/olitreadwell/react-spectrum.git fix-docs-typos
git checkout FETCH_HEAD

The diff is docs-only (13 one-word typo fixes in 10 files). No tests are needed; yarn lint and the docs build are unaffected.

[snowystinger]

Thanks!
Make sure you sign the CLA with the same e-mail that opened the PR https://github.com/adobe/react-spectrum/blob/main/CONTRIBUTING.md#contributor-license-agreement