AI Proofread: Update Breve toggle location

[renatoagds]

Move proofread on top of the AI Assistant panel features and update Breve toggle location

Proposed changes:

• Put Breve toggle location with label.
• Remove check of isPluginSidebarOpened since it's not required.

Other information:

• [ ] Have you written new tests for your changes, if applicable?
• [ ] Have you checked the E2E test CI results, and verified that your changes do not break them?
• [ ] Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Open your editor, nothing should change.
• Activate Breve feature.
• The toggle should live together with the AI FEEDBACK title.