[Perl/perl5] 09da49: improve comment as requested. squash me

[Yves Orton via perl5-changes]

  Branch: refs/heads/yves/consistent_srand
  Home:   https://github.com/Perl/perl5
  Commit: 09da499791126886f4368c0f8c530a4971ce3abc
      
https://github.com/Perl/perl5/commit/09da499791126886f4368c0f8c530a4971ce3abc
  Author: Yves Orton <demer...@gmail.com>
  Date:   2022-08-11 (Thu, 11 Aug 2022)

  Changed paths:
    M pod/perlfunc.pod

  Log Message:
  -----------
  improve comment as requested. squash me

note that PERL_RAND_SEED is non-negative, and some rewording to eliminate
the use of the word "var" or "env" in the perldoc.