Update a Product Metafield

Updates a *Product Metafield*. **Required Fields** * none **Read-Only Fields** * id * These fields can only be modified using the API account that created the metafield: * `namespace` * `key` * `permission_set` * `value` **Usage Notes** * Attempting to modify the `namespace`, `key`, `permission_set`, or `value` field using an API account different from the one used to create those metafields will result in a `403` error message.