Revert "Reinstate testing of Jetty JSP sample on Java 9"

This reverts commit bbca612a57.
StandardJarScanner, which contains the faulty assumption about
URLClassLoader is part of Jasper. Jetty, like Tomcat, uses Jasper for
JSPs so it's also affected.

See gh-10456

spring-boot-samples/spring-boot-sample-jetty-jsp/pom.xml

@@ -82,4 +82,23 @@
 			</plugin>
 		</plugins>
 	</build>
+	<profiles>
+		<profile>
+			<id>java9</id>
+			<activation>
+				<jdk>9</jdk>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.apache.maven.plugins</groupId>
+						<artifactId>maven-surefire-plugin</artifactId>
+						<configuration>
+							<skipTests>true</skipTests>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+	</profiles>
 </project>