Packages: optimize performance to sync package description

Created by: olafurpg

Currently, the sync times for the npm package host is taking ~12hr because we fetch the description for 72k repositories https://sourcegraph.com/site-admin/external-services/RXh0ZXJuYWxTZXJ2aWNlOjMwMzAzNw==

For comparison, the sync time for the Rust package host with 89.1k packages completes in ~3 minutes.

The slow sync times of the npm package host cause problems because they take up CPU/network resources, and they significantly slow down the feedback loop when addressing syncing issues like invalid package names in the database

While it's desirable to have descriptions of npm packages, our current solution is too inefficient to allow running in production on sourcegraph.com. We should disable this feature for now and only re-enable it when we have a more optimized solution.