Bump whitenoise from 4.1.2 to 5.2.0

Bumps [whitenoise](https://github.com/evansd/whitenoise) from 4.1.2 to 5.2.0.
- [Release notes](https://github.com/evansd/whitenoise/releases)
- [Changelog](https://github.com/evansd/whitenoise/blob/master/docs/changelog.rst)
- [Commits](evansd/whitenoise@v4.1.2...v5.2.0)

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

Author: dependabot-preview[bot]

requirements.txt

@@ -12,4 +12,4 @@ psycopg2-binary==2.7.7
 pytz==2018.9
 requests==2.21.0
 urllib3==1.24.2
-whitenoise==4.1.2
+whitenoise==5.2.0