Remove flag to switch Quickoffice component extension to viewer only mode

Edit works reliable enough so we don't need this flag anymore.

BUG=338855
TEST=manual

Review URL: https://codereview.chromium.org/135393007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248112 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248112