cwltool: upgrade to the latest version

[audrium]

closes https://github.com/reanahub/reana-workflow-engine-cwl/issues/187

• [x] reana-dev run-example -w cwl works as expected
• [x] complexity estimation works as expected

[codecov-commenter]

Codecov Report

Merging #192 (56e3cc1) into master (1b571e1) will increase coverage by 0.22%. The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #192      +/-   ##
==========================================
+ Coverage   24.81%   25.04%   +0.22%     
==========================================
  Files          10       10              
  Lines         548      551       +3     
==========================================
+ Hits          136      138       +2     
- Misses        412      413       +1     

Impacted Files	Coverage Δ
reana_workflow_engine_cwl/cwl_reana.py	15.03% <50.00%> (+0.29%)	:arrow_up:
reana_workflow_engine_cwl/tasks.py	71.42% <50.00%> (-1.65%)	:arrow_down: