[Perl/perl5] a9ab5e: pad.h: remove pad_peg (was part of MAD)

[mauke via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: a9ab5eec7b2f8da87868ba19dcc8838a2db182f0
      
https://github.com/Perl/perl5/commit/a9ab5eec7b2f8da87868ba19dcc8838a2db182f0
  Author: Lukas Mai <lukasmai....@gmail.com>
  Date:   2024-02-14 (Wed, 14 Feb 2024)

  Changed paths:
    M pad.c
    M pad.h

  Log Message:
  -----------
  pad.h: remove pad_peg (was part of MAD)

This was missed in b5bbe64ad2ec5141 when most of MAD was removed.
pad_peg() has been a no-op macro ever since.