s390: remove the unneeded select GCC12_NO_ARRAY_BOUNDS

Commit 0da6e5fd

 ("gcc: disable '-Warray-bounds' for gcc-13 too") makes
config GCC11_NO_ARRAY_BOUNDS to be for disabling -Warray-bounds in any gcc
version 11 and upwards, and with that, removes the GCC12_NO_ARRAY_BOUNDS
config as it is now covered by the semantics of GCC11_NO_ARRAY_BOUNDS.

As GCC11_NO_ARRAY_BOUNDS is yes by default, there is no need for the s390
architecture to explicitly select GCC11_NO_ARRAY_BOUNDS. Hence, the select
GCC12_NO_ARRAY_BOUNDS in arch/s390/Kconfig can simply be dropped.

Remove the unneeded "select GCC12_NO_ARRAY_BOUNDS".

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>