[resultui] fix redirect-sw unnecessarily hijacking requests
[resultui] fix redirect-sw unnecessarily hijacking requests

event.respondWith(fetch(event.request)) doesn't do anything and may
cause extra error logging in the console in some cases.

R=nodir, nqmtuan

Change-Id: Ifafa57e568089170e11441ffc719e003a75800af
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2827435
Auto-Submit: Weiwei Lin <968518a24f41fef00b747498600e52b792d06ae0@google.com>
Reviewed-by: Quang Minh Tuan Nguyen <7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com>
Commit-Queue: Quang Minh Tuan Nguyen <7f5d2f4f6ce87649784e35ad551490ab8d89e8eb@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go