[Perl/perl5] 29dfcd: add a mention of smartmatch being deprecated

[Karen Etheridge via perl5-changes]

  Branch: refs/heads/ether/switch-deprecated-perlsyn
  Home:   https://github.com/Perl/perl5
  Commit: 29dfcd593925054c510e072d2a6b263bd04a1b3e
      
https://github.com/Perl/perl5/commit/29dfcd593925054c510e072d2a6b263bd04a1b3e
  Author: Karen Etheridge <et...@cpan.org>
  Date:   2023-04-27 (Thu, 27 Apr 2023)

  Changed paths:
    M pod/perlsyn.pod

  Log Message:
  -----------
  add a mention of smartmatch being deprecated