Updated documentation to clarify target parent management identification

[Brunoga-MS]

…to be targeted

Overview/Summary

Replace this with a brief description of what this Pull Request fixes, changes, etc.

This PR fixes/adds/changes/removes

1. Changed the description of parent mg from "identity, management and connectivity" to "Platform and Landing Zones" to better clarify the targeting. I was made aware of the confusion during the support to issue 328

Breaking Changes

1. NONE

As part of this Pull Request I have

• Read the Contribution Guide and ensured this PR is compliant with the guide
• Checked for duplicate Pull Requests
• Associated it with relevant GitHub Issues or ADO Work Items (Internal Only)
• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Ensured PR tests are passing
• Updated relevant and associated documentation (e.g. Contribution Guide, Docs etc.)

[arjenhuitema]

LGTM