Incomplete rename of focus fields

With PR #1346, names in `dashboards/focus/focus.yaml` are renamed to lowercases. However one line is missing from this rename, and still uses capital letter as shown below. This incomplete rename breaks our dashboard.

https://github.com/aws-solutions-library-samples/cloud-intelligence-dashboards-framework/blob/cd2a7e0c9443b2c64c7ae9a7a86741023794d37a/dashboards/focus/focus.yaml#L5025