Do an after-merge fix

Related to MID-2119 (shadow caching).

infra/prism-impl/src/test/java/com/evolveum/midpoint/prism/query/lang/TestQueryValidation.java

@@ -32,7 +32,7 @@ public class TestQueryValidation extends AbstractPrismTest {
 
     @BeforeSuite
     public void setupDebug() throws SchemaException, SAXException, IOException {
-        PrettyPrinter.setDefaultNamespacePrefix(DEFAULT_NAMESPACE_PREFIX);
+        PrettyPrinter.addDefaultNamespacePrefix(DEFAULT_NAMESPACE_PREFIX);
         PrismTestUtil.resetPrismContext(new PrismInternalTestUtil());
         this.axiomQueryLangService = new AxiomQueryLangServiceImpl(PrismContext.get());
     }