Android: Remove mentions of envsetup.sh from docs

Having it listed in the docs implies that running the script is
necessary to have things work; it's not. Also - fewer instructions the
better!

Change-Id: I993821cc6a11267cdc54fa99075ae5979f622520
Reviewed-on: https://chromium-review.googlesource.com/788132
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518965}
6 files changed