Convert backtick (`) admonition fences to tildes (~)

[ErikSchierboom]

In line with Exercism's spec, we're ensuring that all admonition fences are demarcated with four tildes (~~~~) across all repositories. We will be following up with an org-wide script that can be used to keep this consistent. Problem Specifications has already been updated.

We'll automatically merge this a week from now, but feel free to merge beforehand!

• Spec: https://exercism.org/docs/building/markdown/markdown#h-special-blocks-sometimes-called-admonitions
• Meta issue: Convert backtick (`) admonition fences to tildes (~) exercism#6705

[github-actions]

Thank you for contributing to exercism/elixir 💜 🎉. This is an automated PR comment 🤖 for the maintainers of this repository that helps with the PR review process. You can safely ignore it and wait for a maintainer to review your changes.

Based on the files changed in this PR, it would be good to pay attention to the following details when reviewing the PR:

• General steps

  • 🏆 Does this PR need to receive a label with a reputation modifier (x:size/{tiny,small,medium,large,massive})? (A medium reputation amount is awarded by default, see docs)

• Any exercise changed

  • 👤 Does the author of the PR need to be added as an author or contributor in <exercise>/.meta/config.json (see docs)?
  • 🔬 Do the analyzer and the analyzer comments exist for this exercise? Do they need to be changed?
  • 📜 Does the design file (<exercise>/.meta/design.md) need to be updated to document new implementation decisions?

• Practice exercise changed

  • 🌲 Do prerequisites, practices, and difficulty in config.json need to be updated?
  • 🧑‍🏫 Are the changes in accordance with the community-wide problem specifiations?

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