Clean up policy captions on the policy template list.

These captions are used to generate the administrative templates for
Chrome on Windows and Mac OS X. The captions end up in tab labels and dropdown
lists, and shouldn't have full stops at the end.

BUG=None

Review URL: https://codereview.chromium.org/25245002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225994 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225994