chore(CI): Adjust testing matrix for Nextcloud 33 on stable33

Signed-off-by: Joas Schilling <coding@schilljs.com>

Author: nickvergessen

composer.json

@@ -2,7 +2,7 @@
 	"require-dev": {
 		"bamarni/composer-bin-plugin": "^1.8",
 		"bantu/ini-get-wrapper": "1.0.1",
-		"nextcloud/ocp": "dev-master"
+		"nextcloud/ocp": "dev-stable33"
 	},
 	"config": {
 		"allow-plugins": {