Add week timeframe to Polish locale

[akwodkiewicz]

Pull Request Checklist

Thank you for taking the time to improve Arrow! Before submitting your pull request, please check all appropriate boxes:

• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
• 📚 Updated documentation for changed code.
  (:x: No documentation change needed.)
• ⏩ Code is up-to-date with the master branch.

If you have any questions about your code changes or any of the points above, please submit your questions along with the pull request and we will try our best to help!

Description of Changes

I've added missing week and weeks timeframes to Polish locale and also fixed the grammar errors in the existing entries.

[codecov-io]

Codecov Report

Merging #769 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #769   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           10        10           
  Lines         1696      1681   -15     
  Branches       288       288           
=========================================
- Hits          1696      1681   -15     

Impacted Files	Coverage Δ
arrow/locales.py	100.00% <ø> (ø)
arrow/arrow.py	100.00% <0.00%> (ø)
arrow/parser.py	100.00% <0.00%> (ø)

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[jadchaar]

Looks good thanks for the contribution @akwodkiewicz!

[jadchaar]

Hey @akwodkiewicz, seems like a recent merge that contained some big changes to our testing suite was merged in and thus caused some conflicts. Mind resolving them so we can merge this in?

[systemcatch]

Conflicts don't look to bad, I can help with fixing if need be.

[akwodkiewicz]

Thanks @systemcatch.