Remove metafieldDelete in favor of metafieldsDelete

As of 2025-01 the metafieldDelete Admin API method is being removed. The metafieldsDelete method should be used instead. The former relies on the Metafield GID, while the latter takes an array of Metafield Identifiers composed of ownerId, namspace, and key. Note that the Metafield GID is not an option in metafieldsDelete.