build(deps): bump icalendar from 6.2.0 to 6.3.1

Bumps [icalendar](https://github.com/collective/icalendar) from 6.2.0 to 6.3.1.
- [Release notes](https://github.com/collective/icalendar/releases)
- [Changelog](https://github.com/collective/icalendar/blob/main/CHANGES.rst)
- [Commits](collective/icalendar@v6.2.0...v6.3.1)

---
updated-dependencies:
- dependency-name: icalendar
  dependency-version: 6.3.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -16,7 +16,7 @@ django-select2==8.4.0
 django-simple-history==3.8.0
 django-widget-tweaks==1.5.0
 gunicorn==23.0.0
-icalendar==6.2.0
+icalendar==6.3.1
 Pillow==11.2.1
 psycopg[binary]==3.2.7
 python-decouple==3.8