Updates an existing inventory item's variants by inventory ID.
The updateInventoryVariantFields() function returns a Promise that resolves when the
variant with the specified inventory ID has been updated.
Only the properties passed in the inventory item object will be updated. All other properties will remain the same.
Note: You can also update a variant's inventory by product ID instead of inventory ID using the updateInventoryVariantFieldsByProductId() function. The product ID is the corresponding product ID for the inventory item in a Wix store.
Inventory ID of the item with variants to update.
The inventory information to update in the variant.