Update dependency org.junit.jupiter:junit-jupiter to v6 (#2655)

Author: Goooler

gradle.properties

@@ -30,7 +30,7 @@ VER_SLF4J=[1.6,2.0[
 # Used in multiple places
 VER_DURIAN=1.2.0
 VER_JGIT=7.4.0.202509020913-r
-VER_JUNIT=5.14.1
+VER_JUNIT=6.0.1
 VER_ASSERTJ=3.27.6
 VER_MOCKITO=5.20.0
 VER_SELFIE=2.5.5

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/FreshMarkExtensionTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 DiffPlug
+ * Copyright 2016-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,16 +15,12 @@
  */
 package com.diffplug.gradle.spotless;
 
-import static org.junit.jupiter.api.condition.JRE.JAVA_14;
-
 import java.io.IOException;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.EnabledForJreRange;
 
 class FreshMarkExtensionTest extends GradleIntegrationHarness {
 	@Test
-	@EnabledForJreRange(max = JAVA_14)
 	void integration() throws IOException {
 		setFile("build.gradle").toLines(
 				"plugins {",

testlib/src/test/java/com/diffplug/spotless/java/GoogleJavaFormatStepTest.java

@@ -15,7 +15,6 @@
  */
 package com.diffplug.spotless.java;
 
-import static org.junit.jupiter.api.condition.JRE.JAVA_15;
 import static org.junit.jupiter.api.condition.JRE.JAVA_20;
 import static org.junit.jupiter.api.condition.JRE.JAVA_21;
 
@@ -39,9 +38,8 @@ void jvm13Features() throws Exception {
 	}
 
 	@Test
-	@EnabledForJreRange(max = JAVA_15) // google-java-format requires JRE 11+
 	void behavior18() throws Exception {
-		FormatterStep step = GoogleJavaFormatStep.create("1.8", TestProvisioner.mavenCentral());
+		FormatterStep step = GoogleJavaFormatStep.create(TestProvisioner.mavenCentral());
 		StepHarness.forStep(step)
 				.testResource("java/googlejavaformat/JavaCodeUnformatted.test", "java/googlejavaformat/JavaCodeFormatted18.test")
 				.testResource("java/googlejavaformat/JavaCodeWithLicenseUnformatted.test", "java/googlejavaformat/JavaCodeWithLicenseFormatted.test")