Do not throw error on cancelled session

[domnantas]

I have reduced the session capture rate to 5%. That means 95% of users are not tracked, but they get this in console:

This seems odd, because I think this cancelling is intended, therefore not an error. This piece of code causes the error:

openreplay/tracker/tracker/src/main/app/index.ts

Lines 277 to 281 in 2ce6ff8

	} else { // TODO: handle canceling && 403
	return r.text().then(text => {
	throw new Error(`Server error: ${r.status}. ${text}`);
	});
	}

[PandaCodes]

@domnantas indeed, you mentioned in the pr the reasons why I didn't do it instantly. Please, find the promise solution in the version 3.4.9 - the tracker.start() returns a promise from this moment, and canceling/errors could be handled with .catch. (Still not sure it is the best solution though)
Thanks for kicking me with this contribution!

[domnantas]

I still see 403 and errors being thrown in the console with reduced capture rate