Remove IMAGE_FEATURES setting from agl-image-weston

Remove IMAGE_FEATURES setting from agl-image-weston

This should be set down in the final images if required.
We do not need it in the core image that will be reused.

Signed-off-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Change-Id: Ic694e5a3209336adbb6e558ceb205c7cc306b8d8
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/27168
ci-image-build: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Scott Murray <scott.murray@konsulko.com>