refactor: Unify severity and level for all application errors for Sentry (no-changelog) (#7956)

## Summary
Unify `severity` and `level` for all backend application errors for
Sentry

Follow-up to:
https://github.com/n8n-io/n8n/pull/7914#issuecomment-1840433542

...

#### How to test the change:
1. ...


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers

...


## Review / Merge checklist
- [ ] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [ ] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
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packages/workflow/src/errors/abstract/execution-base.error.ts

@@ -1,4 +1,4 @@
-import type { Functionality, IDataObject, JsonObject, Severity } from '../../Interfaces';
+import type { Functionality, IDataObject, JsonObject } from '../../Interfaces';
 import { ApplicationError } from '../application.error';
 
 interface ExecutionBaseErrorOptions {
@@ -19,8 +19,6 @@ export abstract class ExecutionBaseError extends ApplicationError {
 
 	lineNumber: number | undefined;
 
-	severity: Severity = 'error';
-
 	functionality: Functionality = 'regular';
 
 	constructor(message: string, { cause, errorResponse }: ExecutionBaseErrorOptions = {}) {