chore(deps): bump certifi from 2024.2.2 to 2024.7.4 in /backend

Bumps [certifi](https://github.com/certifi/python-certifi) from 2024.2.2 to 2024.7.4.
- [Commits](certifi/python-certifi@2024.02.02...2024.07.04)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: direct:production
...

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

backend/requirements.txt

@@ -13,7 +13,7 @@ black==24.3.0
     # via piccolo
 cachetools==5.3.3
     # via google-auth
-certifi==2024.2.2
+certifi==2024.7.4
     # via
     #   httpcore
     #   httpx