[chromeperf] Update the instruction to update index setup.
[chromeperf] Update the instruction to update index setup.

Update because appcfg is deprecated.

Change-Id: Iee0aaaa17886afe79d4314abddfc0d625b3c8b42
Reviewed-on: https://chromium-review.googlesource.com/c/catapult/+/3503795
Reviewed-by: John Chen <334fbfbb4df7c78f091ea1b77c69ca6ac731a3f3@chromium.org>
Commit-Queue: Wenbin Zhang <45ad8a1ff616a38a2202fd35571df81897c5f14f@google.com>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult