Remove PO files from repo and update translations

[dominik-zeglen]

I want to merge this change because it tidies repository a little bit and updates translations.

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. Translated strings are extracted to .pot file.
4. Number of API calls is optimized.
5. The changes are tested.
6. Type definitions are up to date.
7. Changes are mentioned in the changelog.

[codecov]

Codecov Report

Merging #409 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #409   +/-   ##
=======================================
  Coverage   72.41%   72.41%           
=======================================
  Files         639      639           
  Lines        7127     7127           
  Branches     1185     1185           
=======================================
  Hits         5161     5161           
  Misses       1725     1725           
  Partials      241      241

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