Update signed exchange test directory reference

The directory was renamed in crrev.com/c/1132835.

Bug: 856530
Change-Id: I34890b24f256048d49bc59f5ba34ec048ce48d1c
Reviewed-on: https://chromium-review.googlesource.com/1133609
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Kunihiko Sakamoto <ksakamoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574481}
1 file changed