[DOCS] Add MongoDB 7 and 8 to the Registry

[TomFern]

Documentation Location

https://docs.semaphoreci.com/using-semaphore/optimization/container-registry#mongodb

Type of Documentation Issue

• Missing documentation
• Incorrect information
• Unclear explanation
• Outdated content
• Broken link
• Code example needs update
• Other (please describe)

Current State

The Semaphore Docker Registry lists MongoDB 6 as the highest supported image. We now have images for versions 7 and 8 availab.e

Requested Changes

Add MongoDB 7 and 8 to the Registry

Suggested Content

Additional Information

Affects Version

• Cloud Semaphore
• Community Edition (specify version): all

[TomFern]

PR: #200