strace.spec.in: remove strace64 subpackage

strace.spec.in: remove strace64 subpackage

strace64 subpackage used to be installed into ppc32 and sparc32
userspace running by a 64-bit kernel to trace 64-bit processes.

As simultaneous decoding of processes running both in 64-bit and 32-bit
personality is fully supported on every architecture with compat kernel
support for quite some time, one can just install a 64-bit strace and
there is no more need for that strace64 kludge.

* strace.spec.in (strace64_arches, copy64, %ifarch %{strace64_arches}):
Remove.