remove deprecated armv7 gyp setting now that all uses have been removed

BUG=234135

Review URL: https://codereview.chromium.org/120123004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242428 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242428