Added plurals tests for DutchLocale

[erwinmintiens]

Pull Request Checklist

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

• [x] 🧪 Added tests for changed code.
• [x] 🛠️ All tests pass when run locally (run tox or make test to find out!).
• [x] 🧹 All linting checks pass when run locally (run tox -e lint or make lint to find out!).
• [x] 📚 Updated documentation for changed code.
• [x] ⏩ 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

Added plural testcases for the DutchLocale class. Relates to #1022

[codecov[bot]]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage :thumbsup:

Coverage data is based on head (9c5f0ce) compared to base (1bba2a8). Patch has no changes to coverable lines.

Additional details and impacted files

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[krisfremen]

@erwinmintiens thanks for improving arrow!