Do not have Enumeratory::Lazy#zip mark result as packed

Fixes [Bug #19569]

Author: jeremyevans

enumerator.c

@@ -2369,7 +2369,6 @@ lazy_zip_arrays_func(VALUE proc_entry, struct MEMO *result, VALUE memos, long me
         rb_ary_push(ary, rb_ary_entry(RARRAY_AREF(arrays, i), count));
     }
     LAZY_MEMO_SET_VALUE(result, ary);
-    LAZY_MEMO_SET_PACKED(result);
     rb_ary_store(memos, memo_index, LONG2NUM(++count));
     return result;
 }

test/ruby/test_lazy_enumerator.rb

@@ -282,6 +282,11 @@ def test_zip_with_block
     assert_equal(3, a.current)
   end
 
+  def test_zip_map_lambda_bug_19569
+    ary = [1, 2, 3].to_enum.lazy.zip([:a, :b, :c]).map(&:last).to_a
+    assert_equal([:a, :b, :c], ary)
+  end
+
   def test_take
     a = Step.new(1..10)
     assert_equal(1, a.take(5).first)