Enable Paketo builder system tests on Java 20

Closes gh-35897

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

@@ -60,7 +60,7 @@ import static org.assertj.core.api.Assertions.entry;
  * @author Scott Frederick
  */
 @ExtendWith({ GradleBuildInjectionExtension.class, GradleBuildExtension.class })
-@EnabledForJreRange(max = JRE.JAVA_18)
+@EnabledForJreRange(max = JRE.JAVA_20)
 class PaketoBuilderTests {
 
 	GradleBuild gradleBuild;