docs: fix throttling rate comment and tweak comcast bandwidth

[mattzeunert]

Summary

Throttling rate is in kilobits not kilobytes.

LH uses a bandwidth of 1638kbps/1.6mpbs by default, so we should recommend using that with comcast too.

[paulirish]

the throttling.md change works for me.

But I'm not sure about the kilobytes => kilobits change.

EDIT: nevermind. Lantern seems to consistently treat "throughput" as bits per second.

[paulirish]

Took another look and Lantern is good.

Also confirmed that DevTools's emulateNetworkConditions speaks in bytes per second.
That leads me to wonder why we never convert our configuration value... My best guess is it's somehow wrapped up in the DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR but that seems very odd... @patrickhulce plz tell me i'm being really dumb here. :)

[patrickhulce]

We do convert our numbers before sending to DevTools, so I think we're all good here.

lighthouse/lighthouse-core/lib/emulation.js

Lines 107 to 110 in 5865c87

	// DevTools expects throughput in bytes per second rather than kbps
	conditions.downloadThroughput = Math.floor(conditions.downloadThroughput * 1024 / 8);
	conditions.uploadThroughput = Math.floor(conditions.uploadThroughput * 1024 / 8);
	return driver.sendCommand('Network.emulateNetworkConditions', conditions);

[patrickhulce]

LGTM!

Nice catch @mattzeunert yeah the lowercase b in Kbps was meant to be the signal for kilobits per second, not sure how we messed that doc string up 😆