remove these indexes in the next major release (8.0.0) - their only consumers (the per-room notification-preference finders) were removed

[github-actions]

{ key: { desktopNotifications: 1 }, sparse: true },
{ key: { mobilePushNotifications: 1 }, sparse: true },
{ key: { emailNotifications: 1 }, sparse: true },

📝 Found in packages/models/src/models/Subscriptions.ts#L49

Commit: 582d25d