Document that the license agent is not upgraded with Calico Enterprise - #2887

Changed pages include:

• index.html - view
• 404.html - view
• archive/index.html - view
• docs/index.html - view
• search/index.html - view
• use-cases/cluster-mesh/index.html - view
• use-cases/egress-access-controls/index.html - view
• use-cases/egress-gateways/index.html - view
• use-cases/microsegmentation/index.html - view
• use-cases/observability/index.html - view

There are more changes not included in the list