Bump prometheus-flask-exporter from 0.18.5 to 0.18.6 in /webapp

Bumps [prometheus-flask-exporter](https://github.com/rycus86/prometheus_flask_exporter) from 0.18.5 to 0.18.6.
- [Release notes](https://github.com/rycus86/prometheus_flask_exporter/releases)
- [Commits](rycus86/prometheus_flask_exporter@0.18.5...0.18.6)

---
updated-dependencies:
- dependency-name: prometheus-flask-exporter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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