Since frontend was moved to the flex runtime, there is no longer
a reason to keep the two separate. Consolidate the two into one
service to reduce deployment complexity.
Change-Id: Ie64c17e1833ed94ac8bff7381963f683d824ca5d
Reviewed-on: https://go-review.googlesource.com/85456
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>