Suppress warning in SpringFailOnTimeoutTests

spring-test/src/test/java/org/springframework/test/context/junit4/spr16716/SpringFailOnTimeoutTests.java

@@ -84,6 +84,7 @@ public class SpringFailOnTimeoutTests {
 		new SpringFailOnTimeout(statement, 100).evaluate();
 	}
 
+	@SuppressWarnings("serial")
 	private static class Boom extends RuntimeException {
 	}