[Perl/perl5] 875327: get rid of running_under_some_shell dead variable

[Nicolas R.]

  Branch: refs/heads/core-p7
  Home:   https://github.com/Perl/perl5
  Commit: 875327342c0694925c0dfd17e9f107c65c46b8a7
      
https://github.com/Perl/perl5/commit/875327342c0694925c0dfd17e9f107c65c46b8a7
  Author: Nicolas R <atoo...@cpan.org>
  Date:   2020-07-08 (Wed, 08 Jul 2020)

  Changed paths:
    M Porting/Glossary
    M README.bs2000
    M pod/perlrun.pod
    M utils/streamzip.PL

  Log Message:
  -----------
  get rid of running_under_some_shell dead variable

round 2:

This is fixing issues from utils/streamzip