elastic_ecs: fix STIX 2.1 results translation

[pcoccoli]

Remove unnecessary result processing that raised the exception for STIX 2.1.

Fixes #1304

[codecov]

Codecov Report

Base: 85.35% // Head: 85.36% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (aa2f9a0) compared to base (a9e5b43).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1306   +/-   ##
========================================
  Coverage    85.35%   85.36%           
========================================
  Files          569      569           
  Lines        42557    42572   +15     
========================================
+ Hits         36323    36340   +17     
+ Misses        6234     6232    -2     

Impacted Files	Coverage Δ
...elastic_ecs/stix_translation/results_translator.py	100.00% <ø> (+4.76%)	⬆️
.../stix_translation/test_elastic_ecs_json_to_stix.py	100.00% <100.00%> (ø)
stix_shifter_utils/utils/helpers.py	62.50% <0.00%> (+2.08%)	⬆️

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