Update documentation in wrapper script to match the changed behavior in install-debian.wheezy.sysroot.py

NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/15001024

git-svn-id: http://src.chromium.org/svn/trunk/src/build@199321 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

linux/install-debian.wheezy.sysroot.wrapper.py

@@ -11,7 +11,6 @@
 #
 # * branding=Chrome
 # * buildtype=Official
-# * target_arch=[matching_arch]
 #
 # and not:
 #