🔧 Remove `remark-gfm` for default footnote handling

[thetrevorharmon]

What does this PR do?

This PR:

• Remove the remark-gfm since gatsby-transformer-remark has a footnotes option.

Does this relate to an open issue?

No

Checklist before merge

• [x] I have prefixed the name of the pull request with an emoji.
• [x] I have run yarn tophat locally to ensure that it builds correctly OR I have verified it builds with a deploy preview.

[netlify[bot]]

✅ Deploy Preview for thetrevorharmon ready!

Name	Link
🔨 Latest commit	a30ec2f28bf8e2a3b4cc677b98c1ebf78fda229f
🔍 Latest deploy log	https://app.netlify.com/sites/thetrevorharmon/deploys/667f5be7cfcd76000866327e
😎 Deploy Preview	https://deploy-preview-216--thetrevorharmon.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 98 Accessibility: 100 Best Practices: 100 SEO: 85 PWA: 60 View the detailed breakdown and full score reports

---

To edit notification comments on pull requests, go to your Netlify site configuration.