Update regs TOC to use list links

[anselmbradford]

regulations listings table of contents uses custom pattern at https://www.consumerfinance.gov/rules-policy/regulations/

It should use a list link pattern instead https://cfpb.github.io/design-system/components/links#list-link

Changes

• Update regs TOC to use list links.

How to test this PR

1. Pull branch and yarn build && ./runserver.sh and visit http://localhost:8000/rules-policy/regulations/ and resize to mobile. Set the date of a reg into the future on admin/regulations3k/effectiveversion/?part=2 to show the nested list.

Screenshots

Before	After

Notes and todos

• We don't currently show it, but there is a nested link list pattern, which should be standardized in the design system.
• Desktop version will have underlines when Update cfpb-design-system, ax-core, cypress, eslint, eslint-plugin-cypress, eslint-plugin-jsdoc, esbuild,snyk, stylelint #8927 goes in.