Bump pillow from 5.1.0 to 6.2.0 in /client

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.1.0 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@5.1.0...6.2.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

client/requirements.txt

@@ -7,7 +7,7 @@ itsdangerous==0.24
 Jinja2==2.10
 MarkupSafe==1.0
 meld3==1.0.2
-Pillow==5.1.0
+Pillow==6.2.0
 PyMsgBox==1.0.6
 PyScreeze==0.1.14
 PyTweening==1.0.3