Update de.yaml month abbreviations

[kross326]

No description provided.

[codecov]

Codecov Report

Merging #408 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #408   +/-   ##
=======================================
  Coverage   94.95%   94.95%           
=======================================
  Files         302      302           
  Lines        2436     2436           
=======================================
  Hits         2313     2313           
  Misses        123      123

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[Gallaecio]

Please, see https://dateparser.readthedocs.io/en/latest/contributing.html#guidelines-for-editing-translation-data