elf: Remove /etc/suid-debug support

Since malloc debug support moved to a different library
(libc_malloc_debug.so), the glibc.malloc.check requires preloading the
debug library to enable it.  It means that suid-debug support has not
been working since 2.34.

To restore its support, it would require to add additional information
and parsing to where to find libc_malloc_debug.so.

It is one thing less that might change AT_SECURE binaries' behavior
due to environment configurations.

Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>