fix(pipeline): add AuthCertName for ESRP cert-based auth

ESRP fails with "AuthCertName should be set" because the service
connection uses cert-based auth but the pipeline only had
AuthSignCertName (signing cert) without AuthCertName (auth cert).
UseMSIAuth:true was also set but ignored since the connection is
cert-based, causing confusion.

Fix for both Authenticode DLL signing and NuGet package signing:
- Remove UseMSIAuth: true (not used by this service connection)
- Add AuthCertName sourced from ESRP_AUTH_CERT_NAME pipeline variable

ADO action required: Add ESRP_AUTH_CERT_NAME pipeline variable
pointing to the authentication certificate name in Key Vault.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: imran-siddique

pipelines/esrp-publish.yml

@@ -384,10 +384,10 @@ stages:
             displayName: 'ESRP Authenticode sign DLLs'
             inputs:
               ConnectedServiceName: 'Agent Governance Toolkit'
-              UseMSIAuth: true
               AppRegistrationClientId: '$(ESRP_CLIENT_ID)'
               AppRegistrationTenantId: '$(MICROSOFT_TENANT_ID)'
               AuthAKVName: '$(ESRP_KEYVAULT_NAME)'
+              AuthCertName: '$(ESRP_AUTH_CERT_NAME)'
               AuthSignCertName: '$(ESRP_CERT_IDENTIFIER)'
               FolderPath: '$(Pipeline.Workspace)\nuget-unsigned'
               Pattern: '*.dll'
@@ -436,10 +436,10 @@ stages:
             displayName: 'ESRP Code Sign NuGet package'
             inputs:
               ConnectedServiceName: 'Agent Governance Toolkit'
-              UseMSIAuth: true
               AppRegistrationClientId: '$(ESRP_CLIENT_ID)'
               AppRegistrationTenantId: '$(MICROSOFT_TENANT_ID)'
               AuthAKVName: '$(ESRP_KEYVAULT_NAME)'
+              AuthCertName: '$(ESRP_AUTH_CERT_NAME)'
               AuthSignCertName: '$(ESRP_CERT_IDENTIFIER)'
               FolderPath: '$(Pipeline.Workspace)\nuget-unsigned'
               Pattern: '*.nupkg'