build: [security] bump werkzeug from 0.15.2 to 0.15.3 (#1640)

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.15.2 to 0.15.3. **This update includes a security fix.**
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](pallets/werkzeug@0.15.2...0.15.3)

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