Fix punctuation and remove a word from extension permission warnings.

BUG=362794
TBR=rdevlin.cronin@chromium.org

Review URL: https://codereview.chromium.org/236233002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264909 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed