Fix gitpython version and remove jsonlines

[damiencarol]

Fix 2 dependencies problems:

1. gitpython don't use a pinned version, switching to a pinned one
   

   django-DefectDojo/requirements.txt

   Line 55 in 920503f

   gitpython>=2.1.13

2. remove useless dependency jsonlines
   

   django-DefectDojo/requirements.txt

   Line 62 in 920503f

   jsonlines==2.0.0 # requred by yarn audit parser

Regarding the 1)

Relevant issue upstream gitpython-developers/GitPython#983

 File "/usr/local/lib/python3.6/site-packages/git/compat.py", line 16, in <module>
    from gitdb.utils.compat import (
ModuleNotFoundError: No module named 'gitdb.utils.compat'

[damiencarol]

@valentijnscholten this is an interesting issue