[Perl/perl5] 434ccf: add missing =cut to sv.h

[iabyn via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 434ccf36bb90d7dfe527c3ecd775983821669b4a
      
https://github.com/Perl/perl5/commit/434ccf36bb90d7dfe527c3ecd775983821669b4a
  Author: David Mitchell <da...@iabyn.com>
  Date:   2022-08-17 (Wed, 17 Aug 2022)

  Changed paths:
    M cv.h

  Log Message:
  -----------
  add missing =cut to sv.h

The just-added CvREFCOUNTED_ANYSV apidoc entry was missing the =cut
at the end.