Bump certifi from 2026.4.22 to 2026.5.20

Bumps [certifi](https://github.com/certifi/python-certifi) from 2026.4.22 to 2026.5.20.
- [Commits](certifi/python-certifi@2026.04.22...2026.05.20)

---
updated-dependencies:
- dependency-name: certifi
  dependency-version: 2026.5.20
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -29,7 +29,7 @@ broadbean==0.15.0
     #   qcodes
 cachebox==5.2.3
     # via deepdiff
-certifi==2026.4.22
+certifi==2026.5.20
     # via requests
 cf-xarray==0.11.1
     # via