Update feature key in instruction data pointer proposal (#373)

proposals/0321-vm-r2-instruction-data-pointer.md

@@ -7,7 +7,7 @@ category: Standard
 type: Core
 status: Review
 created: 2025-07-11
-feature: (fill in with feature key and github tracking issues once accepted)
+feature: 5xXZc66h4UdB6Yq7FzdBxBiRAFMMScMLwHxk2QZDaNZL
 ---
 
 ## Summary