Remove SequentialUpdateChecker in favor of upstream implementation if possible

[goodov]

Look into batching component update checks into a single update request. Upstream support this, but we disable this logic, because:

// Google's ToS do not allow distributing all components. In particular, the
// Widevine plugin must be fetched from Google servers. Brave's update server
// for components handles this as follows: When an update for a Google
// component is requested, the server responds with a HTTP redirect to
// Google's server. The problem is that this only works for update requests
// for single components. But Chromium's default implementation sends a list of
// components in one request, which in Brave's case is a mix of Google and Brave
// components. To solve this, we overwrite Chromium's implementation to perform
// separate update requests instead.

If there's no reasons that block us from batching the update request (fingerprinting, legal, performance, costs), then we can update go-updater to support Brave/non-Brave components in a single request and make it proxy requests to the upstream updater automatically.

See the discussion in brave/brave-core#23169