Update christophwurst/nextcloud requirement from ^17.0 to ^19.0

Updates the requirements on [christophwurst/nextcloud](https://github.com/ChristophWurst/nextcloud_composer) to permit the latest version.
- [Release notes](https://github.com/ChristophWurst/nextcloud_composer/releases)
- [Commits](https://github.com/ChristophWurst/nextcloud_composer/compare/v17.0.0...v19.0.0)

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

composer.json

@@ -3,7 +3,7 @@
 	"type": "project",
 	"license": "AGPLv3",
 	"require-dev": {
-		"christophwurst/nextcloud": "^17.0",
+		"christophwurst/nextcloud": "^19.0",
 		"phpunit/phpunit": "^8",
         "nextcloud/coding-standard": "^0.3.0"
     },