Revert "gddo-server/assets: update banner"

This reverts commit 8691e18f09a943e79d6c67de14c819e5bfbaf1d6.

Reason for revert: split deploy of teeproxy and banner changes

Revert CL 274698.

Change-Id: I611e450d5dd0fd059a6df49b1e1e5a6cb003eefb
Reviewed-on: https://go-review.googlesource.com/c/gddo/+/277112
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>