refactor(core): Stop reporting non-error to sentry (issue 4229454473) (no-changelog) (#7525)

This PR aims to stop reporting issues such as [this
one](https://n8nio.sentry.io/issues/4229454473/events/42b96bfd6a334c15a84499e981cf90eb/?project=4503924908883968).

Github issue / Community forum post (link here to close automatically):

packages/workflow/src/WorkflowErrors.ts

@@ -15,6 +15,7 @@ export class WorkflowOperationError extends ExecutionBaseError {
 
 	constructor(message: string, node?: INode) {
 		super(message, { cause: undefined });
+		this.severity = 'warning';
 		this.name = this.constructor.name;
 		this.node = node;
 		this.timestamp = Date.now();