Remove Jetty p2 repository from Maven build

This reference is not required and would force all JGit consumers to
switch to Maven 3 and Tycho which isn't desirable.

Bug: http://dev.eclipse.org/mhonarc/lists/jgit-dev/msg01687.html
Change-Id: Iecf7c5aad46bb05fce0455cc8127aee2f679848c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

pom.xml

@@ -183,11 +183,6 @@
       <id>jgit-repository</id>
       <url>http://download.eclipse.org/jgit/maven</url>
     </repository>
-    <repository>
-      <id>jetty</id>
-      <layout>p2</layout>
-      <url>http://download.eclipse.org/jetty/updates/jetty-bundles-7.x/${jetty-version}/</url>
-    </repository>
   </repositories>
 
   <build>