meta-ohos-foundation: remove obsolete layer

meta-ohos-foundation is containing recipes for some OpenHarmony components. Due
to the fact that OpenHarmony relies on GN tool which requires complete source
tree for carrying out the build, it was decided to drop recipe-per-component
approach and try a single gn.bbclass based recipe for all interconnected
OpenHarmony components approach instead. That decision renders this layer
obsolete.

Relates: https://git.ostc-eu.org/OSTC/planning/maintenance/-/issues/16



Signed-off-by: robert.drab <robert.drab@huawei.com>