Update create-credential-definition.md

aw-design-diagram/create-credential-definition.md

+```mermaid
 sequenceDiagram
 participant OCM Admin
 participant OCM Attestation Manager
@@ -5,3 +6,4 @@ participant OCM Attestation Manager
   OCM Admin ->> OCM Attestation Manager: Calls the POST method credentialDef with relevant attributes.
   OCM Attestation Manager ->> OCM Admin: Responds with status code 201, with message 'Credential definition created successfully', if credential definition is created on ledger successfully
   end
+```