Update principal-user-registration-sequence.md

aw-design-diagram/principal-user-registration-sequence.md

+```mermaid
 sequenceDiagram
 participant Playstore/Appstore
 participant PCM User
@@ -33,3 +34,4 @@ participant OCM Attestation Manager
   OCM Principal Manager ->> OCM Attestation Manager: Requests Attestation Manager with Principal Credential CredDef to issue credential based on CredDef
   OCM Attestation Manager ->> PCM App: Issues Credential to the individual and the credential gets stored in PCM App's wallet
   end
+```