Removing `undefined` type or `?` specifier.

## Description
SonarCloud reports a violation of rule `typescript:S4782`. Optional property declarations should not use both `?` and `undefined`.

## Sonar Issue
https://sonarcloud.io/project/issues?open=AZ5vYOWvEtPFZsxg7_Xu&id=OWASP_Nest

## Affected Code
```bash
excludedUsernames?: Array | string | null | undefined;
```

## Note
In many file same SonarCloud violation `Consider removing 'undefined' type or '?' specifier, one of them is redundant.`