[phpunit.xml] Fix incorrect nested filter element

Author: pH-7

phpunit.xml.dist

@@ -1,15 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
 <phpunit bootstrap="tests/bootstrap.php" colors="true">
-
     <testsuites>
         <testsuite name="Unit Tests">
             <directory>tests</directory>
         </testsuite>
-
-        <filter>
-            <whitelist>
-                <directory suffix=".php">src</directory>
-            </whitelist>
-        </filter>
     </testsuites>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">src</directory>
+         </whitelist>
+     </filter>
 </phpunit>