Disable PR Relink Button After Milestone Completion in Management Plane API Readiness

[MrJustinB]

Issue Summary:

The issue involves the management plane API readiness process where the link button remains enabled on the "associate Pull Request task", allowing users to update PR link even after the milestone is marked as complete. This leads to inconsistencies in the state of the release plan.

Solution Discussed:

Disable the button to relink the PR once the milestone is completed to prevent further modifications.
Alternatively, if a new PR is added, reset the entire state of the milestone, not just the individual steps, to ensure consistency.

Key Points:

The button should be disabled once the milestone is completed to avoid revalidation and ensure the PR used for SDK generation is final.
If a new PR is added, reset the entire milestone state to maintain consistency.

[maririos]

I will add, the api readiness milestone can't be completed until the PR is merged somewhere (a branch in the private repo for private preview) and in main of the public repo for `public preview, and GA)

[maririos]

@MrJustinB given the High priority, we will try to add it to our next release