Polish "Add Java 14 CI"

See gh-20413

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/junit/GradleCompatibilityExtension.java

@@ -42,7 +42,10 @@ public final class GradleCompatibilityExtension implements TestTemplateInvocatio
 	private static final List<String> GRADLE_VERSIONS;
 
 	static {
-		if (JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_13)) {
+		if (JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_14)) {
+			GRADLE_VERSIONS = Arrays.asList("default");
+		}
+		else if (JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_13)) {
 			GRADLE_VERSIONS = Arrays.asList("6.0.1", "6.1.1", "6.2.2", "default");
 		}
 		else {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/SpringBootPluginIntegrationTests.java

@@ -40,6 +40,7 @@ class SpringBootPluginIntegrationTests {
 
 	final GradleBuild gradleBuild = new GradleBuild();
 
+	@DisabledForJreRange(min = JRE.JAVA_14)
 	@Test
 	void failFastWithVersionOfGradleLowerThanRequired() {
 		BuildResult result = this.gradleBuild.gradleVersion("5.5.1").buildAndFail();