⬆️ Bump pygments from 2.8.1 to 2.15.0 in /server/projects/main

Bumps [pygments](https://github.com/pygments/pygments) from 2.8.1 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.8.1...2.15.0)

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

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

server/projects/main/requirements.txt

@@ -24,7 +24,7 @@ celery-redbeat==2.0.0
 djangorestframework==3.11.2
 coreapi==2.3.3
 Markdown==3.3.4
-Pygments==2.8.1
+Pygments==2.15.0
 django-filter==2.4.0
 django-cors-headers==3.7.0