Fix trailing whitespace.

src/Collection/Iterator/NoChildrenIterator.php

@@ -19,7 +19,7 @@ use RecursiveIterator;
 
 /**
  * An iterator that can be used as an argument for other iterators that require
- * a RecursiveIterator but do not want children. This iterator will 
+ * a RecursiveIterator but do not want children. This iterator will
  * always behave as having no nested items.
  */
 class NoChildrenIterator extends Collection implements RecursiveIterator