serverutil/frontend: remove redundant HTTP->HTTPS redirect handler
serverutil/frontend: remove redundant HTTP->HTTPS redirect handler

The cloud/https package now takes care of this.

Change-Id: I6117c64fe25081b7706cd733c214d1c78d83915b
Reviewed-on: https://upspin-review.googlesource.com/18145
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

upspin/upspin,upspin/upspin