[FIX] sale_product_configurator: allow type False for customValue

Steps to reproduce(locally):
1) Create SO with the product that has a custom value attribute
2) Leave the custom field empty
3) Save SO and open product configurator again
4) Observe TypeError traceback

Reason: customValue is supposed to be string but if value is not set,
it remains False which cause a type error.

After this commit: allow customValue be false

X-original-commit: 4ce49fd
Part-of: odoo#150653

addons/sale_product_configurator/static/src/js/product_template_attribute_line/product_template_attribute_line.js

@@ -41,7 +41,7 @@ export class ProductTemplateAttributeLine extends Component {
             type: String,
             validate: type => ["always", "dynamic", "no_variant"].includes(type),
         },
-        customValue: { type: String, optional: true },
+        customValue: {type: [{value: false}, String], optional: true},
     };
 
     //--------------------------------------------------------------------------