Remove manifest.t, as Dist::Zilla handles all of that

t/manifest.t

@@ -1,13 +0,0 @@
-#!perl -T
-
-use strict;
-use warnings;
-use Test::More;
-
-unless ( $ENV{RELEASE_TESTING} ) {
-    plan( skip_all => "Author tests not required for installation" );
-}
-
-eval "use Test::CheckManifest 0.9";
-plan skip_all => "Test::CheckManifest 0.9 required" if $@;
-ok_manifest();