Update Jetpack connected modal copy

[fditrapani]

Where

1. Start on https://wordpress.com/jetpack/connect
2. Enter a URL for a non-jetpack connected site
3. Add credentials and begin connection

Problem

After you connect your site, we show you a modal where the title is disconnected from the action. Heading and button copy should always pair cohesively, with supporting copy providing additional context.

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] Plugins: The issue concerns the Jetpack plugin, specifically its modal interface during site connection.
• [Feature] Jetpack Connection Errors: This issue relates directly to the user experience when encountering connectivity issues with Jetpack.
• [Feature] Authentication: The problem highlighted pertains to user authentication during the connection process.