Update certego-saas requirement from ~=0.2.0 to ~=0.5.0 in /requirements

Updates the requirements on [certego-saas](https://github.com/certego/certego-saas) to permit the latest version.
- [Release notes](https://github.com/certego/certego-saas/releases)
- [Commits](certego/certego-saas@0.2.0...0.5.0)

---
updated-dependencies:
- dependency-name: certego-saas
  dependency-type: direct:production
...

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

requirements/project-requirements.txt

@@ -5,4 +5,4 @@ psycopg2-binary~=2.9.2
 slack-sdk~=3.12.0
 djangorestframework~=3.13.1
 drf-spectacular~=0.26.1
-certego-saas~=0.2.0
+certego-saas~=0.5.0