resolve problem with SSDEEP use in hashing-algorithm-ov

[emmanvg]

Eliminates problem in stix2 where an object using an ssdeep hash in 2.1 would use the lowercase variant. closes #391

[codecov-io]

Codecov Report

Merging #393 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #393   +/-   ##
=======================================
  Coverage   98.44%   98.44%           
=======================================
  Files         127      127           
  Lines       14613    14627   +14     
=======================================
+ Hits        14386    14400   +14     
  Misses        227      227           

Impacted Files	Coverage Δ
stix2/patterns.py	99.33% <ø> (ø)
stix2/test/v21/test_pattern_expressions.py	100.00% <ø> (ø)
stix2/properties.py	98.42% <100.00%> (+<0.01%)	⬆️
stix2/test/v20/test_observed_data.py	100.00% <100.00%> (ø)
stix2/test/v21/test_observed_data.py	100.00% <100.00%> (ø)

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[emmanvg]

@clenk I rebased, and build passed now...

[clenk]

LGTM, thanks @emmanvg!