Bump spatie/icalendar-generator from 2.9.2 to 3.0.0 in /backend

Bumps [spatie/icalendar-generator](https://github.com/spatie/icalendar-generator) from 2.9.2 to 3.0.0.
- [Release notes](https://github.com/spatie/icalendar-generator/releases)
- [Changelog](https://github.com/spatie/icalendar-generator/blob/main/CHANGELOG.md)
- [Commits](spatie/icalendar-generator@2.9.2...3.0.0)

---
updated-dependencies:
- dependency-name: spatie/icalendar-generator
  dependency-version: 3.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

backend/composer.json

@@ -22,7 +22,7 @@
         "nette/php-generator": "^4.0",
         "php-open-source-saver/jwt-auth": "^2.1",
         "sentry/sentry-laravel": "^4.13",
-        "spatie/icalendar-generator": "^2.8",
+        "spatie/icalendar-generator": "^3.0",
         "spatie/laravel-data": "^4.11",
         "spatie/laravel-webhook-server": "^3.8",
         "stripe/stripe-php": "^17.0"