Added 'sku' field to Standalone Price Deleted Message

The Standalone Price Deleted Message now includes a new field, sku, which helps you identify the associated SKU when you delete a Standalone Price.

Changes:

• [API] Added field sku to Standalone Price Deleted Message.
• [GraphQL API] Changed the StandalonePriceDeleted type:
  • Added the sku field to the StandalonePriceDeleted type.

The following changes were introduced in terms of GraphQL SDL:

extend type StandalonePriceDeleted {
  sku: String
}