Remove unnecessary `extends Object` from generic

See gh-38739

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/TestPrintStream.java

@@ -37,7 +37,7 @@ import org.springframework.util.FileCopyUtils;
  */
 class TestPrintStream extends PrintStream implements AssertProvider<PrintStreamAssert> {
 
-	private final Class<? extends Object> testClass;
+	private final Class<?> testClass;
 
 	TestPrintStream(Object testInstance) {
 		super(new ByteArrayOutputStream());