Fix Gotify provider to use generic webhook type

Changed from unsupported 'gotify' type to 'generic' webhook.
Gotify API token is embedded in the URL.

bootstrap/notification-provider.yaml

@@ -4,10 +4,8 @@ metadata:
   name: gotify
   namespace: flux-system
 spec:
-  type: gotify
+  type: generic
-  address: http://gotify.gotify.svc.cluster.local
+  address: http://gotify.gotify.svc.cluster.local/message?token=APMvTuncQJmm6vd
-  secretRef:
-    name: gotify-token
 ---
 apiVersion: notification.toolkit.fluxcd.io/v1beta3
 kind: Alert