chore: Replace Logger.warn/1 with Logger.warning/2

[abshierjoel]

Closes #493

Elixir 1.15 deprecated Logger.warn/1 in favor of the new Logger.warning/2. @tjchambers proposed a solution to maintain compatibility for Elixir < 1.10 but since the readme already lists >= 1.10 as a requirement, I figured this change could just be made directly.

[abshierjoel]

Apologies, I missed that #495 was already opened and resolves this with the bump in Elixir version. No need for this PR.

[subzero10]

Apologies, I missed that #495 was already opened and resolves this with the bump in Elixir version. No need for this PR.

No worries! Thanks for helping out! Since you are on the topic, can you please have a look at #495 and see why the tests are failing?

[abshierjoel]

@subzero10
For sure! I'll take a look tomorrow morning and see if I can get it working.