Update tzlocal to v4.x and remove pytz dependency

[outa]

Changes

• remove pytz dependency and replace it with zoneinfo from stdlib (rationale: https://pytz-deprecation-shim.readthedocs.io/en/latest/index.html)
• update tzlocal

Caveats

There are some differences between pytz's is_dst and datetime's fold argument: https://pytz-deprecation-shim.readthedocs.io/en/latest/migration.html#semantic-differences-between-is-dst-and-fold

I had to adapt a test for this. I don't know what the implications of this would be for jrnl. Please decide if this is reasonable for you.

Closes: #1338

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[micahellison]

Hi @outa, thank you for working on this! I just merged the develop branch in after our 3.0 release to update the poetry.lock file, and I still see a couple issues in the Mac tests on this PR. Let us know if you have any questions about those or would like any help.

[outa]

Hi Micah! So after you merged the develop branch, the tests were failing on my laptop (using Ubuntu). However in the Gitlab pipeline they passed for some reason. I think we are running into this issue: regebro/tzlocal#131

I am trying to work around that now. However debugging the macOS tests is a bit difficult for me, because I don't have access to a macOS machine. Is there some way to test in a mac environment before pushing changes?

[wren]

This was a tricky one, but you nailed it. Thank you!