Refine ServiceInstanceMetaData wording in profile.md

[gberche-orange]

Sorry @rsampaio for my late review of #721 commit 743278585a1f3db08c55d1fba469149f0a6ccd66 please find improvement suggestion in this PR

What is the problem this PR solves?

This PR fixes the following issues that I believe #721 introduced:

• dedicated section was breaking the TOC structure being inserted in the middle of service Metadata
• seems to implied that ServiceInstanceMetaData could be returned from Catalog endpoint

Checklist:

• [ ] The swagger.yaml doc has been updated with any required changes: only formatting changes
• [ ] The openapi.yaml doc has been updated with any required changes: only formatting changes

[jberkhahn]

minor nit, then LGTM