owners: use `@sourcegraph/frontend-platform-devs` team
Created by: valerybugakov
Context
To limit the noise of GitHub notifications relevant only for engineers, we created a separate GitHub team @sourcegraph/frontend-platform-devs, which will be used in OWNERS
files.
Test plan
Create a PR that changes files in one of the packages with frontend-platform OWNERS
. It should notify @sourcegraph/frontend-platform-devs instead of @sourcegraph/frontend-platform.