Bump s3transfer from 0.3.2 to 0.3.3

Bumps [s3transfer](https://github.com/boto/s3transfer) from 0.3.2 to 0.3.3.
- [Release notes](https://github.com/boto/s3transfer/releases)
- [Changelog](https://github.com/boto/s3transfer/blob/develop/CHANGELOG.rst)
- [Commits](https://github.com/boto/s3transfer/compare/0.3.2...0.3.3)

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

requirements.txt

@@ -20,7 +20,7 @@ pycountry-convert==0.7.2
 pycountry==19.8.18
 python-dateutil==2.8.1
 requests==2.22.0
-s3transfer==0.3.2
+s3transfer==0.3.3
 setuptools==44.0.0
 six==1.14.0
 transip==2.0.0