fix: add attribution to permitted uses, trim utm_source_platform description

Author: jamesandersen

docs/specification/event-context.md

@@ -140,7 +140,7 @@ regulations.
 Implementations **MUST**:
 
 - Only use event context data for the purposes of conversion measurement,
-  reporting, and analytics
+  reporting, attribution, and analytics
 - **NOT** transmit personally identifiable information (e.g., email addresses,
   phone numbers, names) through any field in this extension
 - Comply with applicable consent requirements for advertising and marketing

source/schemas/shopping/event_context.json

@@ -33,7 +33,7 @@
             "utm_content": { "type": "string" },
             "utm_term": { "type": "string" },
             "utm_id": { "type": "string" },
-            "utm_source_platform": { "type": "string", "description": "Advertising platform that served the ad (e.g., Google, Meta, TikTok). Corresponds to the utm_source_platform parameter used by GA4 and other analytics tools." }
+            "utm_source_platform": { "type": "string" }
           }
         },
         "custom": {