correct env varible name

Author: polinaouk

articles/aks/csi-secrets-store-identity-access.md

@@ -105,7 +105,7 @@ Azure AD workload identity (preview) is supported on both Windows and Linux clus
         usePodIdentity: "false"
         useVMManagedIdentity: "false"          
         clientID: "${USER_ASSIGNED_CLIENT_ID}" # Setting this to use workload identity
-        keyvaultName: ${$KEYVAULT_NAME}       # Set to the name of your key vault
+        keyvaultName: ${KEYVAULT_NAME}       # Set to the name of your key vault
         cloudName: ""                         # [OPTIONAL for Azure] if not provided, the Azure environment defaults to AzurePublicCloud
         objects:  |
           array: