Bring design of the saas-trial-illustration into alignment with design guidelines

The following discussion from !760 (merged) needs to be addressed:

@tauriedavis:

Thanks! Looks like this followed a different process than Im used to. I noticed that it doesn't work so well on different backgrounds:

We have new guidelines for the color palette to work with light/dark themes. @jeldergl since our other illustrations have a similar issue, are we fine merging this as a first iteration and opening an issue to align it with our guides? That way, we don't block the work the growth team is working on.

@jeldergl:

I haven't seen this before @tauriedavis. I agree, I don't want to block work for growth so we can merge.

@dreedy would you mind opening up a followup issue in this project so that the design can be updated? Is this part of an experiment or a final flow? I'm thinking that if it's an experiment it'd be a good idea to keep them in a separate repo until the flow is finalized.

FWIW I unchecked the task in the description because this doesn't follow the current guides.

Where does it live?

Trial registration	In-app trial step 1	In-app trial step 2
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