Followup: Duo Chat included reference tokens tyles

Followup from a comment by @sdejonge:

Once this become visually stable within the DuoChat experimental component, we may want to either:

1. Define the blue variant as design tokens for GlToken so we may use something like <gl-token variant="something">
2. Use feedback.info (or whatever is appropriate) semantic design tokens for these contextual overrides

Definitely non-blocking of this visual improvement, but something we should create a follow-up for to ensure that this color usage is not forgotten as part of the design token rollout gitlab-org&13200 (closed) and removal of deprecated colors.