fixed plugin.xml example in javadoc that leads to warnings when copy&pasted

Change-Id: Ic134456ded541b2771601f6fe92b45ae2369d92c
Signed-off-by: Christian Dietrich <christian.dietrich@itemis.de>
diff --git a/org.eclipse.debug.core/core/org/eclipse/debug/core/model/IStepFilter.java b/org.eclipse.debug.core/core/org/eclipse/debug/core/model/IStepFilter.java
index 4183815..1178f07 100644
--- a/org.eclipse.debug.core/core/org/eclipse/debug/core/model/IStepFilter.java
+++ b/org.eclipse.debug.core/core/org/eclipse/debug/core/model/IStepFilter.java
@@ -20,10 +20,10 @@
  *
  * <pre>
  *  &lt;extension point=&quot;org.eclipse.debug.core.stepFilters&quot;&gt;
- *   &lt;stepFilters
+ *   &lt;stepFilter
  *    class=&quot;com.example.ExampleStepFilters&quot;
  *    modelIdentifier=&quot;com.example.debug.model&quot;&gt;
- *   &lt;/stepFilters&gt;
+ *   &lt;/stepFilter&gt;
  * &lt;/extension&gt;
  * </pre>
  * <p>