Remove use of deprecated Domain API (#3762)

Use of this feature [has been discouraged for a long time](https://nodejs.org/api/domain.html).

Since most of our code is now bubbling through async, we aren't really getting these "vendor errors" anymore.

Errors that _do_ bubble up through the services have been reported to Sentry since #3706, though they seem to be missing a bunch of their stack traces. Sentry also seems to be combining unrelated internal errors. (https://github.com/badges/shields/issues/3709#issuecomment-514299441) Maybe this will help.