Fix types in complex numbers

[angelikatyborska]

Reported on the forum: http://forum.exercism.org/t/mismatch-between-spec-and-test-on-complex-numbers/10850

I left abs as returning float because :math.sqrt always returns a float. But maybe that doesn't matter... it wouldn't break the test to return an integer from that function if the decimal part is equal to zero. assert_delta_in, used for all assertions, allows mixing up integers and floats.

[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?

---

Automated comment created by PR Commenter 🤖.

[jiegillet]

Cool, it doesn't hurt to be more general.
I think I would also use number for abs so that all real types are the same. It's conceivable to have an implementation that returns an integer, it's unlikely but not incorrect.