Convert property names to camel case

[MAILPOET-1796]

tests/integration/API/JSON/v1/SegmentsTest.php

@@ -10,9 +10,9 @@ use MailPoet\Models\Subscriber;
 use MailPoet\Models\SubscriberSegment;
 
 class SegmentsTest extends \MailPoetTest {
-  public $segment_3;
-  public $segment_2;
-  public $segment_1;
+  public $segment3;
+  public $segment2;
+  public $segment1;
 
   /** @var Segments */
   private $endpoint;