Describes where the Shadowmask settings are located if SupportedRenderingFeatures.overridesShadowmask is set to true.
Override this property if the Shadowmask settings are being overridden by the SRP, and you want the user to be able to find the new location for it.
Returns an empty string by default, which means that if the Shadowmask settings are fully removed for the user, nothing needs to be done.