qspawn: remove Perl 5.16.x leak workaround
It seems no longer necessary to workaround this Perl 5.16.3 bug
after the removal of anonymous subs from all of our internal
code in
https://public-inbox.org/meta/
20191225075104.22184-1-e@80x24.org/
Tested with repeated clones (both aborted and completed)
in a CentOS 7.x VM which was once able to reproduce leaks
before the workaround appeared in
2fc42236f72ad16a
("qspawn: workaround Perl 5.16.3 leak, re-enable Deflater")
Cc: Konstantin Ryabitsev <konstantin@linuxfoundation.org>