Add missing import for util.function to spring-oxm

XStreamMarshaller uses the class SingletonSupplier from this package.
diff --git a/spring-oxm-5.2.8.RELEASE/pom.xml b/spring-oxm-5.2.8.RELEASE/pom.xml
index 6e6ee19..787cebf 100644
--- a/spring-oxm-5.2.8.RELEASE/pom.xml
+++ b/spring-oxm-5.2.8.RELEASE/pom.xml
@@ -91,6 +91,7 @@
             org.springframework.core.type.classreading;version="[${pkgVersion},5.3)",
             org.springframework.core.type.filter;version="[${pkgVersion},5.3)",
             org.springframework.util;version="[${pkgVersion},5.3)",
+            org.springframework.util.function;version="[${pkgVersion},5.3)",
             org.springframework.util.xml;version="[${pkgVersion},5.3)",
             org.w3c.dom,
             org.w3c.dom.ls,