Bump pillow from 4.1.1 to 6.2.0 in /example

Bumps [pillow](https://github.com/python-pillow/Pillow) from 4.1.1 to 6.2.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](python-pillow/Pillow@4.1.1...6.2.0)

Signed-off-by: dependabot[bot] <support@github.com>

example/requirements.txt

@@ -7,7 +7,7 @@ pyprind==2.9.9
 coveralls==1.1
 filemagic==1.6
 unidecode==0.4.20
-pillow==4.1.1
+pillow==6.2.0
 django-storages==1.7.1
 boto3==1.9.209
 -e ../