Update Metadata Ingestion topic in the Connectors doc

[kiran1287]

• Add an introductory paragraph explaining what a Service connection is and why it's needed before the steps begin.
• Restructure steps with explicit numbered lists and bold UI element names for easier scanning
• Rename steps to be more action-oriented: "Select the Service", "Create a New Service", "Select the Connector"
• Replace inline note about Service name immutability with a callout component
• Tighten step copy to be more direct and consistent in tone