Update xarray requirement from >=0.16,<0.21 to >=0.16,<2023.2

[dependabot[bot]]

Updates the requirements on xarray to permit the latest version.

Changelog

Sourced from xarray's changelog.

How to issue an xarray release in 16 easy steps

Time required: about an hour.

These instructions assume that upstream refers to the main repository:

$ git remote -v
{...}
upstream        https://github.com/pydata/xarray (fetch)
upstream        https://github.com/pydata/xarray (push)

1. Ensure your main branch is synced to upstream:

   git switch main
   git pull upstream main
   

2. Add a list of contributors with:

   git log "$(git tag --sort=v:refname | tail -1).." --format=%aN | sort -u | perl -pe 's/\n/$1, /'
   

   This will return the number of contributors:

   git log "$(git tag --sort=v:refname | tail -1).." --format=%aN | sort -u | wc -l
   

3. Write a release summary: ~50 words describing the high level features. This will be used in the release emails, tweets, GitHub release notes, etc.
4. Look over whats-new.rst and the docs. Make sure "What's New" is complete (check the date!) and add the release summary at the top. Things to watch out for:
   • Important new features should be highlighted towards the top.
   • Function/method references should include links to the API docs.
   • Sometimes notes get added in the wrong section of whats-new, typically due to a bad merge. Check for these before a release by using git diff, e.g., git diff v{YYYY.MM.X-1} whats-new.rst where {YYYY.MM.X-1} is the previous release.
5. Open a PR with the release summary and whatsnew changes; in particular the release headline should get feedback from the team on what's important to include.
6. After merging, again ensure your main branch is synced to upstream:

   git pull upstream main
   

7. If you have any doubts, run the full test suite one final time!

   pytest
   

8. Check that the ReadTheDocs build is passing on the main branch.

... (truncated)

Commits

• d0bfd00 v2023.01.0 whats-new (#7440)
• 522ee22 explain keep_attrs in docstring of apply_ufunc (#7445)
• b741d83 Add sentence to open_dataset docstring (#7438)
• b589f6b pin scipy version in doc environment (#7436)
• 6c5840e Improve performance for backend datetime handling (#7374)
• 4f3128b fix typo (#7433)
• 17933e7 Add lazy backend ASV test (#7426)
• f3b7c69 Pull Request Labeler - Workaround sync-labels bug (#7431)
• 2ef82c5 see also : groupby in resample doc and vice-versa (#7425)
• d6d2450 Some alignment optimizations (#7382)
• Additional commits viewable in compare view

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