docs: adjust delete technical user documentation

[Phil91]

Description

Adjusting error codes for the technical user delete

Why

To give an overview of the possible error messages of the backend

Issue

Refs: eclipse-tractusx/portal-backend#986

Backend PR

eclipse-tractusx/portal-backend#995

Checklist

• I have followed the contributing guidelines
• I have performed IP checks for added or updated 3rd party libraries
• I have created and linked IP issues or requested their creation by a committer
• I have added copyright and license headers, footers (for .md files) or files (for images)
• I have performed a self-review of my own code
• I have successfully tested my changes locally
• I have added tests that prove my changes work
• I have checked that new and existing tests pass locally with my changes
• [x ] I have commented my code, particularly in hard-to-understand areas

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud