build(deps): bump werkzeug from 0.13 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.13 to 0.15.3.
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](pallets/werkzeug@0.13...0.15.3)

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

Author: dependabot[bot]

requirements.txt

@@ -3,4 +3,4 @@ flask>=0.12.3
 itsdangerous==0.24
 Jinja2==2.10.1
 MarkupSafe==1.0
-Werkzeug==0.13
+Werkzeug==0.15.3