I figured this out and thought I'd leave the solution for those
seeking this out in the future. Basically you just use mod_headers to
unset the headers. The following snippet can be done globally or
within a vhost.
# Hide/Remove the Passenger Headers
Header always unset "X-Powered-By"
Header always unset "X-Runtime"
I found that the quotes and [always] were necessary for this to work
properly. fyi, I'm hiding the headers in response to a security audit
that requested we remove this information.
-John