docs: use device variant tag for product id submissions

.github/ISSUE_TEMPLATE/product-id.yml

@@ -1,7 +1,7 @@
 name: Product details
 description: Report a new product id that matches an existing config
 title: Report a match for <config file name>
-labels: ["device improvement"]
+labels: ["device variant"]
 body:
   - type: markdown
     attributes: