Deprecate s390-linux-gnu (31bit)

Deprecate s390-linux-gnu (31bit)

The next linux 6.19 release will remove support for compat syscalls on s390x with those commits:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0d79affa31cbee477a45642efc49957d05466307
0d79affa31cb Merge branch 'compat-removal'
4ac286c4a8d9 s390/syscalls: Switch to generic system call table generation
f4e1f1b1379d s390/syscalls: Remove system call table pointer from thread_struct
3db5cf935471 s390/uapi: Remove 31 bit support from uapi header files
8e0b986c59c6 s390: Remove compat support
169ebcbb9082 tools: Remove s390 compat support
7afb095df3e3 s390/syscalls: Add pt_regs parameter to SYSCALL_DEFINE0() syscall wrapper
b2da5f6400b4 s390/kvm: Use psw32_t instead of psw_compat_t
8c633c78c23a s390/ptrace: Rename psw_t32 to psw32_t

This patch also removes s390-linux-gnu (31bit) from build-many-glibcs.py.
Then the next update of syscall numbers for Linux 6.19 won't change
sysdeps/unix/sysv/linux/s390/s390-32/arch-syscall.h
Reviewed-by: Andreas K. Huettel <dilfridge@gentoo.org>