Removed hardcoded year 2018 from tests (#539)

[hb9hnt]

Fixes #539

Description of the Change

Replaced the hardcoded year 2018 with datetime.now().year in all four tests which failed.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• changelog entry added to CHANGELOG.md
• author name in AUTHORS (Already included in another pull request.)

[codecov]

Codecov Report

Merging #541 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #541      +/-   ##
==========================================
+ Coverage   95.46%   95.47%   +<.01%     
==========================================
  Files          54       54              
  Lines        2802     2804       +2     
==========================================
+ Hits         2675     2677       +2     
  Misses        127      127

Impacted Files	Coverage Δ
example/tests/unit/test_default_drf_serializers.py	100% <100%> (ø)	⬆️
example/tests/test_views.py	100% <100%> (ø)	⬆️

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[n2ygk]

Thanks for this contribution @PUREMATH. Please add your name to AUTHORS for this PR since the other has not yet been merged. This will be an easy merge once you've done that. Thanks!