filter_gdb.in: __syscall_cancel_arch is just in a syscall

filter_gdb.in: __syscall_cancel_arch is just in a syscall

Since glibc 2.41 some extra syscall_cancel frames are inserted before
that actual syscall is made. Just filter out __syscall_cancel_arch
from the gdb output and replace it with "in syscall ..." to make the
regtest .exp match.

https://bugs.kde.org/show_bug.cgi?id=502126

(cherry picked from commit f3f30becff5851b0d0b2caa7e96e661c7889f7d1)