Remove setting of PLACK_ENV

This should no longer be required as MountPSGI has been updated to set
PLACK_ENV.

Author: ssoriche

lib/MetaCPAN/API.pm

@@ -26,10 +26,6 @@ use MetaCPAN::Script::Runner ();
 use Search::Elasticsearch    ();
 use Try::Tiny qw( catch try );
 
-# MountPSGI doesn't set PLACK_ENV, so Plack::Util::load_psgi defaults to development.
-# Hack around that until MountPSGI is fixed.
-$ENV{PLACK_ENV} ||= $ENV{'MOJO_MODE'} || 'development';
-
 has es => sub {
     return Search::Elasticsearch->new(
         client => '2_0::Direct',