Fix expected result for failing test

Expected boxes is actually 1 because
 * Item 3 fits unrotated
 * Item 7s fit next to each other rotated

Box:

+--------------+
|              |
|              | 3
|              | 6
|              | 0
|              |
+--------------+
     675

3  +----+
3  |    +-------+
5  | #3 |  #7   | 2
.  |    +-------+ 5
2  |    |  #7   | 4
8  +----+-------+
    335.28+330.2
      = 665.4

~15mm spare width, ~10mm spare length

The #7s could also fit unrotated (they're narrower than #3 and total depth is less than when rotated)

tests/PackerTest.php

@@ -338,7 +338,7 @@ public function testIssue6() {
  $packer->addItem(new TestItem('Item 7', 330.2, 127, 101.6, 1));
  $packedBoxes = $packer->pack();
 
- self::assertEquals(2, $packedBoxes->count());
+ self::assertEquals(1, $packedBoxes->count());
 
  }