Issue 3668 link fixes

[anisa-hawes]

This PR resolves the following broken links:

The first is in the EN lesson finding-places-world-historical-gazetteer

• The problem link is:
  • https://whgazetteer.org/accounts/register/
• Replaced with:
  • https://whgazetteer.org/accounts/login/

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The second and third are both found across our research pages (en/research, es/investigacion, fr/recherche and pt/pesquisa)

• The second problem link is:
  • https://ach.org/blog/2021/09/fall-2021-programming-historian-book-club
• Replaced with:
  • https://ach.org/news/2021/09/fall-2021-programming-historian-book-club/

--

• The third problem link is
  • https://ach.org/blog/2022/02/ach-programming-historian-workshop-on-twine-in-the-classroom/
• Replaced with:
  • https://ach.org/news/2022/02/ach-programming-historian-workshop-on-twine-in-the-classroom/

Closes #3668

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