Replace expect()->notEquals() with verify()->notEquals()

codeception/verify 2.1 removed support for expect()->notEquals() so we need
to replace it with verify()->notEquals().

[MAILPOET-5664]

mailpoet/tests/unit/Util/SecurityTest.php

@@ -26,7 +26,7 @@ class SecurityTest extends \MailPoetUnitTest {
   public function testItGeneratesRandomHash() {
     $hash1 = Security::generateHash();
     $hash2 = Security::generateHash();
-    expect($hash1)->notEquals($hash2);
+    verify($hash1)->notEquals($hash2);
     verify(strlen($hash1))->equals(Security::HASH_LENGTH);
   }