Revert "usagestats: use Amplitude HTTP API endpoint"
Created by: jhchabran
Reverts sourcegraph/sourcegraph#25324
Context
https://sourcegraph.slack.com/archives/C02FLQDD3TQ/p1632985048088500
@sourcegraph/frontend-platform there's a linter failure that @attfarhan don't know how to reproduce locally. Also, there's a puppeteer failure that was introduced in https://buildkite.com/sourcegraph/sourcegraph/builds/110082#97bb92b0-b154-4353-b794-2af7cd1b50eb/101-188