android envsetup: Stop setting branding=Chrome buildtype=Official.

They are now set by the internal build script that also sets
CHROME_ANDROID_OFFICIAL_BUILD
( https://chrome-internal-review.googlesource.com/154265 ).

No intended behavior change.

BUG=330631
R=yfriedman@chromium.org

Review URL: https://codereview.chromium.org/159143003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250296 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250296