5.15 doesn't work with gcc 13 and we'll be replacing 5.15 with a new kernel
version later in the release cycle. Drop 5.15 now so we can move forward
with gcc 13 and we'll add a new kernel version later.
(From OE-Core rev: e30b37776d16cfd4ce7f79746427ccd95b306059)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>