Bump flask-cors from 3.0.3 to 3.0.9

Bumps [flask-cors](https://github.com/corydolphin/flask-cors) from 3.0.3 to 3.0.9.
- [Release notes](https://github.com/corydolphin/flask-cors/releases)
- [Changelog](https://github.com/corydolphin/flask-cors/blob/master/CHANGELOG.md)
- [Commits](corydolphin/flask-cors@3.0.3...3.0.9)

---
updated-dependencies:
- dependency-name: flask-cors
  dependency-type: direct:production
...

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

requirements.txt

@@ -1,5 +1,5 @@
 Flask==0.12.2
 Flask-Compress==1.4.0
-Flask-Cors==3.0.3
+Flask-Cors==3.0.9
 greenlet==0.4.12
 gunicorn==19.9.0