Remove KUKSA.val server from Flutter images

Remove KUKSA.val server from Flutter images

Remove KUKSA.val server packagegroup from Flutter demo images now that
all the applications have been converted to using the databroker.

Bug-AGL: SPEC-4762

Change-Id: I50237b668bd7b6aac61bf6d893b14e7f5591760f
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29245
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>