When two headings have the same name the anchor links always link to the first one

[renebrandel]

Describe the bug

When a page has the same heading twice, we don't enumerate them (See how "Legacy" is both under ".signIn" and ".signUp"?) and if I click on any one after the first heading, it scrolls back to the first one. 5:19 In the previous doc, we used to have "#legacy-1" and "#legacy-2" etc. if there more than one to ensure uniqueness.

To Reproduce Steps to reproduce the behavior:

1. Go to https://docs.amplify.aws/react/build-a-backend/auth/auth-migration-guide/#legacy
2. Click on "Legacy" under "Auth.signIn"
3. Get scrolled to "Legacy" under "Auth.signUp"

Expected behavior

Expected: Scrolls to "Legacy" under "Auth.signIn"

Screenshots

https://github.com/aws-amplify/docs/assets/4989523/3550ee56-254f-48ba-8602-69768a19ded2