Ensure the XMLStreamWriter is closed after use

Co-authored-by: Christian Stein <sormuras@gmail.com>
(cherry picked from commit 6a4cb06)

junit-platform-reporting/src/main/java/org/junit/platform/reporting/legacy/xml/XmlReportWriter.java

@@ -115,10 +115,12 @@ private boolean shouldInclude(TestPlan testPlan, TestIdentifier testIdentifier)
 	private void writeXmlReport(TestIdentifier testIdentifier, Map<TestIdentifier, AggregatedTestResult> tests,
 			Writer out) throws XMLStreamException {
 
-		new XmlReport(out).write(testIdentifier, tests);
+		try (XmlReport report = new XmlReport(out)) {
+			report.write(testIdentifier, tests);
+		}
 	}
 
-	class XmlReport implements AutoCloseable {
+	private class XmlReport implements AutoCloseable {
 
 		private final XMLStreamWriter xml;
 		private final ReplacingWriter out;