Bump werkzeug from 0.11.15 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.11.15 to 0.15.3.
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](https://github.com/pallets/werkzeug/compare/0.11.15...0.15.3)

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

requirements.txt

@@ -1,5 +1,5 @@
 APScheduler==3.2.0
-werkzeug==0.11.15
+werkzeug==0.15.3
 Flask==1.0
 requests==2.20.0
 lxml==4.4.2