ftw(): Do not check the maxfds argument against OPEN_MAX.

Apart from the fact that nothing should have OPEN_MAX as a limit (as opposed
to RLIMIT_NOFILE from getrlimit() or _SC_OPEN_MAX from sysconf()), POSIX
does not require us to check this. POSIX does have a requirement on the
application that maxfds not exceed {OPEN_MAX}, but does not require the
implementation to check it ("may fail").

PR: 95239