[Perl/perl5] e4afee: don't clear IOK on @{"_<$file"} entries when a dbs...

[Tony Cook via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: e4afee5bc9d5b14a4d9a02eff8c153831edd0547
      
https://github.com/Perl/perl5/commit/e4afee5bc9d5b14a4d9a02eff8c153831edd0547
  Author: Tony Cook <t...@develop-help.com>
  Date:   2023-10-20 (Fri, 20 Oct 2023)

  Changed paths:
    M lib/perl5db.t
    M op.c

  Log Message:
  -----------
  don't clear IOK on @{"_<$file"} entries when a dbstate is freed

These are meant to be IOK even when non-breakable, and I broke that
when fixing #19198.

Fixes #21564