Pull #3003: fix unused stream in DefaultPluginXmlFactory#write

Author: Vincent Potucek

impl/maven-impl/src/test/java/org/apache/maven/impl/DefaultPluginXmlFactoryTest.java

@@ -22,6 +22,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 
+import org.apache.maven.api.annotations.Nonnull;
 import org.apache.maven.api.plugin.descriptor.PluginDescriptor;
 import org.apache.maven.api.services.xml.XmlReaderException;
 import org.apache.maven.api.services.xml.XmlReaderRequest;
@@ -227,7 +228,7 @@ void shouldThrowXmlReaderExceptionOnMalformedXml() {
 
         XmlReaderException exception = assertThrows(XmlReaderException.class, () -> sut.read(request));
         assertTrue(exception.getMessage().contains("Unable to read plugin"));
-        assertTrue(exception.getCause() instanceof Exception);
+        assertInstanceOf(Exception.class, exception.getCause());
     }