SLING-8321 - The XSSFilterImpl component cannot start on IBM's J9 JVM

* embedded xml-apis 1.4.01, since it's anyways a dependency of the
already embedded antisamy module; this makes sure that the
org.w3c.dom.ElementTraversal class is part of the bundle, rather
than relying on what the JVM provides, given that the class was only
added to the JRE starting from Java 9
diff --git a/pom.xml b/pom.xml
index c58d4a2..cce4771 100644
--- a/pom.xml
+++ b/pom.xml
@@ -112,7 +112,8 @@
                         <Embed-Dependency>
                             antisamy;inline=true,
                             esapi;inline=true,
-                            encoder;inline=true
+                            encoder;inline=true,
+                            xml-apis;inline=true
                         </Embed-Dependency>
                     </instructions>
                 </configuration>