Fix failing tests.

TestPluginThree is now autoloaded by composer. We can no longer use that
plugin to test autoloading registration. Switch the autoload tests to
use TestPluginFive which is not in the autoloader.

tests/TestCase/Core/PluginTest.php

@@ -77,12 +77,12 @@ class PluginTest extends TestCase
      */
     public function testLoadSingleWithAutoload()
     {
-        $this->assertFalse(class_exists('Company\TestPluginThree\Utility\Hello'));
-        Plugin::load('Company/TestPluginThree', [
+        $this->assertFalse(class_exists('Company\TestPluginFive\Utility\Hello'));
+        Plugin::load('Company/TestPluginFive', [
             'autoload' => true,
         ]);
         $this->assertTrue(
-            class_exists('Company\TestPluginThree\Utility\Hello'),
+            class_exists('Company\TestPluginFive\Utility\Hello'),
             'Class should be loaded'
         );
     }
@@ -94,7 +94,6 @@ class PluginTest extends TestCase
      */
     public function testLoadSingleWithAutoloadAndBootstrap()
     {
-        $this->assertFalse(class_exists('Company\TestPluginFive\Utility\Hello'));
         Plugin::load(
             'Company/TestPluginFive',
             [