Remove deprecated page onboardingServiceProvider

[MaximilianHauer]

Description

The following page was created as a first draft in the past but is not needed anymore https://portal.int.catena-x.net/onboardingServiceProvider please delete this page

Acceptance Criteria

• [ ] onboardingServiceProvider and every related link is removed
• [ ] if links are found they are replaced/adjusted with ManagementOnboardingServiceProvider

Additional Information

[MaximilianHauer]

@oyo fyi