rollbar: Remove call to SetServerRoot

The rollbar ui has stopped correctly parsing/displaying our project
frames within the stacktrace. This is *not* due to the recent update
to the rollbar-go package, I was able to see this on master at the time
too. I suspect this was introduced when being used in a go module project.

Author: mmlb

log/internal/rollbar/rollbar.go

@@ -28,7 +28,6 @@ func Setup(l *zap.SugaredLogger, service string) func() {
 
 	v := getVersion()
 	rollbar.SetCodeVersion(v)
-	rollbar.SetServerRoot("/" + service)
 
 	enable := true
 	if os.Getenv("ROLLBAR_DISABLE") != "" {