Update issue-credential-sequence.md

aw-design-diagram/issue-credential-sequence.md

+```mermaid
 sequenceDiagram
 participant PCM User
 participant PCM App
@@ -10,3 +11,4 @@ participant OCM Attestation Manager
   PCM App ->> OCM Attestation Manager: Sends acknowledgement
   OCM Attestation Manager ->> PCM App: Accepts the acknowledgement on accept-request API, and issues the Verifiable Credential, which gets stored in PCM wallet.
   end
+  ```