Update copyright header dates to 2020 (GSA 8)

[swaterkamp]

Checklist:

• [N/A] Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #2019 into gsa-8.0 will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           gsa-8.0    #2019      +/-   ##
===========================================
- Coverage    43.75%   43.74%   -0.01%     
===========================================
  Files          983      983              
  Lines        22837    22841       +4     
  Branches      6466     6490      +24     
===========================================
  Hits          9992     9992              
- Misses       11648    11652       +4     
  Partials      1197     1197

Impacted Files	Coverage Δ
gsa/src/gmp/models/settings.js	100% <ø> (ø)	⬆️
gsa/src/web/components/chart/utils/arc.js	95.38% <ø> (ø)	⬆️
gsa/src/gmp/cancel.js	100% <ø> (ø)	⬆️
gsa/src/gmp/commands/testing.js	100% <ø> (ø)	⬆️
gsa/src/gmp/commands/users.js	25.45% <ø> (ø)	⬆️
gsa/src/gmp/commands/tickets.js	94.73% <ø> (ø)	⬆️
gsa/src/gmp/models/scanconfig.js	95.58% <ø> (ø)	⬆️
gsa/src/gmp/models/filter/convert.js	100% <ø> (ø)	⬆️
gsa/src/gmp/http/transform/xml.js	94.44% <ø> (ø)	⬆️
gsa/src/gmp/http/response.js	80% <ø> (ø)	⬆️
... and 186 more

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