fix(dashboard): Fix error due to ProductVariantPrice custom fields

Relates to #3909. This commit fixes the actual error that prevents the
page from loading at all.

A follow-up will then enable interacting with the custom fields via the Dashboard UI.

packages/dashboard/src/app/routes/_authenticated/_product-variants/product-variants.graphql.ts

@@ -88,7 +88,6 @@ export const productVariantDetailDocument = graphql(
                 prices {
                     currencyCode
                     price
-                    customFields
                 }
                 trackInventory
                 outOfStockThreshold