[Perl/perl5] f4ab8b: Remove pointless use-after-free assert

[Dagfinn Ilmari Mannsåker via perl5-changes]

  Branch: refs/heads/remove-use-after-op-free
  Home:   https://github.com/Perl/perl5
  Commit: f4ab8bdcb8c467b00a9382a3c7ee60da1f7e4696
      
https://github.com/Perl/perl5/commit/f4ab8bdcb8c467b00a9382a3c7ee60da1f7e4696
  Author: Dagfinn Ilmari Mannsåker <ilm...@ilmari.org>
  Date:   2023-09-19 (Tue, 19 Sep 2023)

  Changed paths:
    M class.c

  Log Message:
  -----------
  Remove pointless use-after-free assert

While op_free() doesn't actually free the op, but adds it to the
slab's freelist and marks it as freed, that's not obvious when reading
the code. Also, if op_free() fails to do its job, we have bigger
problems than just here.