Improve "ago" translation to Greek

[pothitos]

Pull Request Checklist

• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
• 🧹 All linting checks pass when run locally (run tox -e lint or make lint to find out!).
• 📚 Updated documentation for changed code.
• ⏩ Code is up-to-date with the master branch.

Description of Changes

Hello and thanks for this library! While trying to migrate from humanize package to arrow, I executed

>>> arrow.get('2013-05-11T21:23:58.970460+07:00').humanize()
'11 years ago'
>>> arrow.get('2013-05-11T21:23:58.970460+07:00').humanize(locale='el')
'11 χρόνια πριν'

The later is printed by humanize as

'πριν από 11 χρόνια'

which is more natural/correct in Greek.

https://github.com/python-humanize/humanize/blob/4da8299fdcf9ad0c56be082b42ee7bee14ee4c4e/src/humanize/locale/el_GR/LC_MESSAGES/humanize.po#L344

Other than that, I fixed Greek abbreviated May accent, so as to be aligned with the full name 15 lines above.

[jadchaar]

Hi @pothitos would it be possible to add a unit test for this change?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (87a1a77) to head (01769dd).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #1184   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           10        10           
  Lines         2326      2323    -3     
  Branches       400       357   -43     
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- Hits          2326      2323    -3     

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[pothitos]

Sure, Jad! Done!

[jadchaar]

LGTM!