Remove/update obsolete 403 & 404 specific tracking code

There is some code in the D8 version of the module that was added in the Drupal 6 era and this code doesn't seem to be of any use today. And it can actually cause (Google) bots to crawl pages that don't exist.

The code was added because:

403 tracking seems not possible in a dynamic way, because hook_footer seems to be skipped... :-(.

hass

In D8 this is no longer the case and possibly D7 as well.

The code was added/updated in these commits
* http://cgit.drupalcode.org/google_analytics/commit/?h=6.x-1.x&id=01a2588...
* http://cgit.drupalcode.org/google_analytics/commit/?h=6.x-1.x&id=7122d4f...
for this particular issue:
* https://www.drupal.org/node/226054

In a later commit, a URL from the Google Analytics help pages was added, and from that URL the author got inspiration for that code; and I've dug through web.archive.org and found this:
* https://web.archive.org/web/20111130011930/http://www.google.com/support...
and by the looks of it, that code isn't of any use today. Probably that code should be completely removed, but I'm not sure, maybe something else can be used instead.