[Perl/perl5] 545f6e: op/sub.t: Cancel watchdog when done

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 545f6e3fd67ed8b75305cfcc59305eddbaca1bf8
      
https://github.com/Perl/perl5/commit/545f6e3fd67ed8b75305cfcc59305eddbaca1bf8
  Author: Karl Williamson <k...@cpan.org>
  Date:   2023-07-03 (Mon, 03 Jul 2023)

  Changed paths:
    M t/op/sub.t

  Log Message:
  -----------
  op/sub.t: Cancel watchdog when done

A watchdog timer should be cancelled after the test(s) it guards.
Otherwise, when someone adds new tests after it in the file, and doesn't
notice that the tests are under the watchdog, those new tests can fail.
These failures may be intermittent, only happening under heavy load.