Enable Paketo builder system tests on Java 18

Closes gh-32296

spring-boot-system-tests/spring-boot-image-tests/src/systemTest/java/org/springframework/boot/image/paketo/PaketoBuilderTests.java

@@ -61,7 +61,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Scott Frederick
  */
 @ExtendWith({ GradleBuildInjectionExtension.class, GradleBuildExtension.class })
-@EnabledForJreRange(min = JRE.JAVA_8, max = JRE.JAVA_17)
+@EnabledForJreRange(min = JRE.JAVA_8, max = JRE.JAVA_18)
 class PaketoBuilderTests {
 
 	GradleBuild gradleBuild;