flavours/linux/local.conf.sample: Remove av96-root-files append

The layer was restructured and all the BSP support is now provided
through the machine configuration.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

flavours/linux/local.conf.sample

@@ -249,5 +249,3 @@ PACKAGECONFIG_append_pn-qemu-system-native = " sdl"
 # track the version of this file when it was generated. This can safely be ignored if
 # this doesn't mean anything to you.
 CONF_VERSION = "1"
-
-IMAGE_INSTALL_append_stm32mp1-av96 = " av96-root-files"