chore(CI): Adjust testing matrix for Nextcloud 31 on stable31

Signed-off-by: Joas Schilling <[email protected]>

Author: nickvergessen

composer.json

@@ -12,7 +12,7 @@
 		"phpunit/phpunit": "^9.5",
 		"nextcloud/coding-standard": "^1.0.0",
 		"vimeo/psalm": "^5.20.0",
-		"nextcloud/ocp": "dev-master"
+		"nextcloud/ocp": "dev-stable31"
 	},
 	"config": {
 		"optimize-autoloader": true,