update the doc link in internal_arthitecture.md (#7966)
update the doc link in internal_arthitecture.md (#7966)

* update the doc link in internal_arthitecture.md
* address reviewer's comment to remove out-dated wrapper

Signed-off-by: Luke Chen <a747209bc9e65a9d7dd7589245c91b7bed721b13@gmail.com>
GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,alileza/prometheus,alileza/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,alileza/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus