fix: added api-definitions product

Author: Kapil Gowru

fern/docs.yml

@@ -53,7 +53,7 @@ products:
   - display-name: API Definitions
     path: ./products/api-def/api-def.yml
     icon: fa-regular fa-book
-    image: ./images/product-switcher/apireference-light.png
+    image: ./images/product-switcher/openapi-definition-light.png
     slug: api-definitions
 
   - display-name: OpenAPI