chore(core): Add missing message translation (#324)

Co-authored-by: Samundra Shrestha <[email protected]>

packages/core/src/i18n/messages/en.json

@@ -46,6 +46,7 @@
     "no-active-tax-zone": "The active tax zone could not be determined. Ensure a default tax zone is set for the current channel.",
     "no-search-plugin-configured": "No search plugin has been configured",
     "no-valid-channel-specified": "No valid channel was specified (ensure the 'vendure-token' header was specified in the request)",
+    "order-already-has-customer": "This Order already has a Customer associated with it",
     "order-contents-may-only-be-modified-in-addingitems-state": "Order contents may only be modified when in the \"AddingItems\" state",
     "order-does-not-contain-line-with-id": "This order does not contain an OrderLine with the id { id }",
     "order-item-quantity-must-be-positive": "{ quantity } is not a valid quantity for an OrderItem",