docs(changelog): Add the link to the new changelog location

[guanlan]

No description provided.

[subnetmarco]

I would instead keep adding new versions and link to the specific file:

## 3.6.0

[Read the CHANGELOG](https://github.com/Kong/kong/blob/master/changelog/3.6.0/3.6.0.md) for this version.

## 3.5.0

[Read the CHANGELOG](https://github.com/Kong/kong/blob/master/changelog/3.5.0/3.5.0.md) for this version.

[chronolaw]

Tracking by KAG-4666, a new PR will fix this issue.