Temporary workaround for Checkstyle bug

Attempting to name a variable in an "instanceof pattern" the same as
a field results in a Checkstyle violation similar to the following if
the "instanceof pattern matching" is located within a constructor.

Reference to instance variable 'document' needs "this.". [RequireThis]

See gh-28188

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

@@ -50,8 +50,8 @@ class DomContentHandler implements ContentHandler {
 	 */
 	DomContentHandler(Node node) {
 		this.node = node;
-		if (node instanceof Document document) {
-			this.document = document;
+		if (node instanceof Document doc) {
+			this.document = doc;
 		}
 		else {
 			this.document = node.getOwnerDocument();