fix: #7372 Trigger onAction on Space key when selectionMode is none

[jsmitrah]

Closes #7372

✅ 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:

• Set selectionMode="none" on the Tree and focus a tree item.
• Press Space and verify onAction triggers (or the node expands) instead of doing nothing.

🧢 Your Project: