Removes the old download feedback string from the context menu

The reporting feature should work via the tab modal dialog / settings. Removing the old download feedback string from the context menu.

BUG=312533

Review URL: https://codereview.chromium.org/166223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251848 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251848