downgraded gitpython in requirements

[MauriceHendrix]

downgraded gitpython in requirements, to latest version that supports python 3.6 as weblab deployment uses ubuntu 18.04 with python 3.6

[codecov[bot]]

Codecov Report

Merging #448 (9141fb4) into master (e15b55d) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 9141fb4 differs from pull request most recent head d0fda20. Consider uploading reports for the commit d0fda20 to get more accurate results

@@           Coverage Diff            @@
##           master     #448    +/-   ##
========================================
  Coverage   96.15%   96.15%            
========================================
  Files          77       77            
  Lines        4473     4473            
  Branches      496      738   +242     
========================================
  Hits         4301     4301            
  Misses        122      122            
  Partials       50       50            

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