Bump drf-spectacular from 0.26.2 to 0.26.4 in /server

Bumps [drf-spectacular](https://github.com/tfranzel/drf-spectacular) from 0.26.2 to 0.26.4.
- [Release notes](https://github.com/tfranzel/drf-spectacular/releases)
- [Changelog](https://github.com/tfranzel/drf-spectacular/blob/master/CHANGELOG.rst)
- [Commits](tfranzel/drf-spectacular@0.26.2...0.26.4)

---
updated-dependencies:
- dependency-name: drf-spectacular
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

server/requirements.txt

@@ -14,4 +14,4 @@ tzdata==2023.3
 whitenoise==6.4.0
 celery==5.2.7
 redis==4.5.5
-drf-spectacular==0.26.2
+drf-spectacular==0.26.4