URL Cleanup - upgrade to more modern Xalan namespace

See gh-22678

spring-core/src/main/java/org/springframework/util/xml/TransformerUtils.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -67,7 +67,7 @@ public abstract class TransformerUtils {
 		transformer.setOutputProperty(OutputKeys.INDENT, "yes");
 		try {
 			// Xalan-specific, but this is the most common XSLT engine in any case
-			transformer.setOutputProperty("{https://xml.apache.org/xslt}indent-amount", String.valueOf(indentAmount));
+			transformer.setOutputProperty("{http://xml.apache.org/xalan}indent-amount", String.valueOf(indentAmount));
 		}
 		catch (IllegalArgumentException ignored) {
 		}

spring-core/src/test/java/org/springframework/util/xml/TransformerUtilsTests.java

 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,8 @@ import org.junit.Test;
 import static org.junit.Assert.*;
 
 /**
+ * Unit tests for {@link TransformerUtils}.
+ *
  * @author Rick Evans
  * @author Arjen Poutsma
  */
@@ -42,7 +44,7 @@ public class TransformerUtilsTests {
 		String indent = transformer.getOutputProperty(OutputKeys.INDENT);
 		assertNotNull(indent);
 		assertEquals("yes", indent);
-		String indentAmount = transformer.getOutputProperty("{https://xml.apache.org/xslt}indent-amount");
+		String indentAmount = transformer.getOutputProperty("{http://xml.apache.org/xalan}indent-amount");
 		assertNotNull(indentAmount);
 		assertEquals(String.valueOf(TransformerUtils.DEFAULT_INDENT_AMOUNT), indentAmount);
 	}
@@ -55,7 +57,7 @@ public class TransformerUtilsTests {
 		String indent = transformer.getOutputProperty(OutputKeys.INDENT);
 		assertNotNull(indent);
 		assertEquals("yes", indent);
-		String indentAmount = transformer.getOutputProperty("{https://xml.apache.org/xslt}indent-amount");
+		String indentAmount = transformer.getOutputProperty("{http://xml.apache.org/xalan}indent-amount");
 		assertNotNull(indentAmount);
 		assertEquals(indentAmountProperty, indentAmount);
 	}