Bump mailchimp3 from 3.0.7 to 3.0.9

Bumps [mailchimp3](https://github.com/charlesthk/python-mailchimp) from 3.0.7 to 3.0.9.
- [Release notes](https://github.com/charlesthk/python-mailchimp/releases)
- [Commits](https://github.com/charlesthk/python-mailchimp/commits

)

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

requirements.txt

@@ -39,7 +39,7 @@ djangorestframework==3.9.2
 djangorestframework-api-key==1.3.0
 django==2.1.11
 gunicorn==19.9.0
-mailchimp3==3.0.7
+mailchimp3==3.0.9
 mistune==0.8.4
 Pillow==5.4.1
 psycopg2==2.7.3.1