drop rng-tools from arm-base and disk-base

rng-tools was dropped from standard comps group recently,
so it's no longer installed by default. Lets remove it from here as well
to get arm and server images building again.

Signed-off-by: Kevin Fenzi <kevin@scrye.com>

fedora-arm-base.ks

@@ -27,7 +27,6 @@ dracut-config-generic
 # install tools needed to manage and boot arm systems
 @arm-tools
 -uboot-images-armv8
-rng-tools
 chrony
 extlinux-bootloader
 bcm283x-firmware

fedora-disk-base.ks

@@ -39,7 +39,6 @@ dracut-config-generic
 -dracut-config-rescue
 # install tools needed to manage and boot arm systems
 @arm-tools
-rng-tools
 chrony
 bcm283x-firmware
 initial-setup