Bump s3transfer from 0.15.0 to 0.16.0

Bumps [s3transfer](https://github.com/boto/s3transfer) from 0.15.0 to 0.16.0.
- [Changelog](https://github.com/boto/s3transfer/blob/develop/CHANGELOG.rst)
- [Commits](boto/s3transfer@0.15.0...0.16.0)

---
updated-dependencies:
- dependency-name: s3transfer
  dependency-version: 0.16.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -82,7 +82,7 @@ django-pageblocks==1.3.0  # pyup: <2.0.0
 django-quizblock==1.3.2
 django-simple-captcha==0.6.2
 gunicorn==23.0.0
-s3transfer==0.15.0
+s3transfer==0.16.0
 jmespath==1.0.1
 
 botocore>=1.15.0,<1.42.0