Fix `forbid-docs-links` errors

Created by: umpox

Description

Rule enabled in this PR: https://github.com/sourcegraph/sourcegraph/pull/32205

Slack context: https://sourcegraph.slack.com/archives/C0C324C91/p1641855680027300

We should be using /help in place of docs.sourcegraph.com for links in-product. /help will automatically version docs in the URL to serve a cached version-correct docsite

Test plan

Run eslint - expect no errors