Adjust Mermaid color scheme for more shapes

Follow up to: !2452 (merged).

Not every mermaid shape is a rect tag. Some use the polygon tag. This MR rolls the style out to more shapes.

• Before (https://docs.gitlab.com/ee/development/documentation/site_architecture/deployment_process.html#documentation-pages-deployment):

  

• After (http://eread-adjust-more-mermaid-shape-colors.178.62.207.141.nip.io/ee/development/documentation/site_architecture/deployment_process.html#documentation-pages-deployment):

  

CC @claytoncornell @oregand just FYI.