Update logoElastic to meet brand guidelines

[ryankeairns]

Recently, when updating the favicon for Kibana, I learned that the cluster logo should always show the white outline.

While adding the new header variations to EUI's Figma library, I noticed that the cluster logo on the dark header does not adhere to these guidelines.

Jess has confirmed that the white outline should be included which, ultimately, means we need to update the underlying logoElastic SVG.