docs: remove broken links from 'In the wild'

[BrianCurrie]

📝 Documentation

• Remove two broken demo links from 'In the wild' section

[BrianCurrie]

Slack link seems dead too #1801

[williaster]

Thanks @BrianCurrie 🙏 And yes the d3 slack channel hasn't been monitored / used well (and has limitations with messages expiring since they use the free plan).

Any interest in replacing that link in this PR with visx discussions which we now use instead? https://github.com/airbnb/visx/discussions

[BrianCurrie]

@williaster no worries! I went ahead and pushed the updated link to discussions.

I noticed the Travis CI build status badge seems to be breaking. I'm getting some text decoration between the links below which may be unintended too. Willing to add an update for those in this PR if that would work for you?

[williaster]

Hey @BrianCurrie CI should be running for the PR now, I'd be surprised if it failed. for first-time contributors to a project, CI has to be approved to run - sorry for the delay! thanks for the slack => discussions update 🙏

[williaster]

CI looks good, thanks again!

[github-actions]

🎉 This PR is included in version v3.9.0 of the packages modified 🎉