meta-app-framework: update af-main SRCREV

meta-app-framework: update af-main SRCREV

Update app-framework-main SRCREV in af-main recipe to pick up:

f8cee78 Fix uninstall of widgets without icons
f8f2338 Improve use of systemd's states

Bug-AGL: SPEC-3323, SPEC-3401

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I35f6fcb8677bd3d5d49e588d03f5868249532baa
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/24584
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>