Update comments for related to un-exporting the variable.

Author: ianwallen

docs/pipelines/agents/docker.md

@@ -325,7 +325,7 @@ Next, create the Dockerfile.
         AZP_TOKEN=$(az account get-access-token --query accessToken --output tsv)
         echo "Token retrieved"
  
-        # Ensure credentials are not visible to the agent by ensuring it is a local variable only
+        # Ensure credentials are not visible to the agent by un-exporting the variable
         export -n AZP_CLIENTSECRET
       fi
 
@@ -339,7 +339,7 @@ Next, create the Dockerfile.
       fi
       echo -n "${AZP_TOKEN}" > "${AZP_TOKEN_FILE}"
 
-      # Ensure credentials are not visible to the agent by ensuring it is a local variable only
+      # Ensure credentials are not visible to the agent by un-exporting the variable
       export -n AZP_TOKEN
     }