Revise API Management references in README

[nourshaker-msft]

Since the focus on this repository is on AI Gateway architectural pattern, moving the extra links by simonkurtz-MSFT into the extra resources at the bottom of the README.md

Purpose

Since this repo is focused on AI Gateway architectural pattern, moving the additional links into the extra resources section

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe: