Remove trailing whitespace

Author: greg0ire

UPGRADE.md

@@ -39,7 +39,7 @@ services:
     and so no longer have a ``$this->container`` property. You *can* manually
     implement this interface. Or, a better idea is to update your fixtures
     to use dependency injection:
-    
+
 ```diff
 class MyFixture extends Fixture
 {
@@ -61,7 +61,7 @@ class MyFixture extends Fixture
 * The base ``Fixture`` class no longer implements ``DependentFixtureInterface``.
     If you want to have a ``getDependencies()`` method, be sure to implement
     this interface explicitly:
-    
+
 ```diff
 + use Doctrine\Common\DataFixtures\DependentFixtureInterface;