Upgrade to Kotlin 1.5.0-RC

Closes gh-26080
Closes gh-25498

gradle.properties

@@ -4,7 +4,7 @@ org.gradle.caching=true
 org.gradle.parallel=true
 org.gradle.jvmargs=-Xmx2g -Dfile.encoding=UTF-8
 
-kotlinVersion=1.4.31
+kotlinVersion=1.5.0-RC
 tomcatVersion=9.0.45
 
 kotlin.stdlib.default.dependency=false

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -30,7 +30,7 @@ dependencies {
 	implementation("org.apache.commons:commons-compress")
 	implementation("org.springframework:spring-core")
 
-	optional("org.jetbrains.kotlin:kotlin-gradle-plugin:1.3.50")
+	optional("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")
 
 	testImplementation(project(":spring-boot-project:spring-boot-tools:spring-boot-test-support"))
 	testImplementation("org.assertj:assertj-core")

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/JarIntegrationTests.java

@@ -25,8 +25,6 @@ import java.util.jar.JarFile;
 import java.util.stream.Collectors;
 
 import org.junit.jupiter.api.TestTemplate;
-import org.junit.jupiter.api.condition.DisabledForJreRange;
-import org.junit.jupiter.api.condition.JRE;
 import org.junit.jupiter.api.extension.ExtendWith;
 
 import org.springframework.boot.loader.tools.FileUtils;
@@ -249,7 +247,6 @@ class JarIntegrationTests extends AbstractArchiveIntegrationTests {
 		});
 	}
 
-	@DisabledForJreRange(min = JRE.JAVA_16) // Remove this once Kotlin supports Java 16
 	@TestTemplate
 	void whenAProjectUsesKotlinItsModuleMetadataIsRepackagedIntoBootInfClasses(MavenBuild mavenBuild) {
 		mavenBuild.project("jar-with-kotlin-module").execute((project) -> {