chore: update the technical user creation documentation

[Phil91]

Description

Adjusted the documentation for the technical user creation process to align with the newly created backend process

Why

The portal backend changed the process to support the creation of technical users that are only visible to the offer

Issue

Refs: #453

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
• I have commented my code, particularly in hard-to-understand areas

[sonarqubecloud]

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 SonarQube Cloud