Use shield icon for 'Security' section in admin settings

[pmaier1]

A shield icon is now available to use in the settings #28580. Please use it for the 'Security' section in the admin settings.

@tomneedham? or @PVince81 to find an assignment, please. Would like to get this into 10.0.3.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.