[doc] Fix location of upb's message accessor API

PiperOrigin-RevId: 527187842

Author: protobuf-github-bot

docs/wrapping-upb.md

@@ -235,7 +235,7 @@ APIs to do this do not exist yet.
 To use MiniTable-based access:
 
 1. Load and access MiniDescriptors data using the interfaces in upb/mini_table.h.
-2. Access message data using the interfaces in upb/msg_accessors.h.
+2. Access message data using the interfaces in upb/message/accessors.h.
 
 ## Memory Management