[headless] update dependencies

briar-headless/build.gradle

 plugins {
 	id 'java'
 	id 'idea'
-	id 'org.jetbrains.kotlin.jvm' version '1.3.21'
-	id 'org.jetbrains.kotlin.kapt' version '1.3.21'
+	id 'org.jetbrains.kotlin.jvm' version '1.3.31'
+	id 'org.jetbrains.kotlin.kapt' version '1.3.31'
 	id 'witness'
 }
 apply from: 'witness.gradle'
@@ -14,25 +14,27 @@ dependencies {
 	implementation project(path: ':briar-core', configuration: 'default')
 	implementation project(path: ':bramble-java', configuration: 'default')
 
-	implementation 'io.javalin:javalin:2.7.0'
-	implementation 'org.slf4j:slf4j-simple:1.7.25'
+	implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.3.31'
+	implementation 'io.javalin:javalin:2.8.0'
+	implementation 'org.slf4j:slf4j-simple:1.7.26'
 	implementation 'com.fasterxml.jackson.core:jackson-databind:2.9.8'
-	implementation 'com.github.ajalt:clikt:1.6.0'
+	implementation 'com.github.ajalt:clikt:2.0.0'
 
-	kapt 'com.google.dagger:dagger-compiler:2.22.1'
+	def daggerVersion = '2.22.1'
+	kapt "com.google.dagger:dagger-compiler:$daggerVersion"
 
 	testImplementation project(path: ':bramble-api', configuration: 'testOutput')
 	testImplementation project(path: ':bramble-core', configuration: 'testOutput')
 
-	def junitVersion = '5.3.1'
+	def junitVersion = '5.4.2'
 	testImplementation "org.junit.jupiter:junit-jupiter-api:$junitVersion"
 	testImplementation "org.junit.jupiter:junit-jupiter-params:$junitVersion"
 	testRuntime "org.junit.jupiter:junit-jupiter-engine:$junitVersion"
-	testImplementation "io.mockk:mockk:1.9.2"
-	testImplementation "org.skyscreamer:jsonassert:1.5.0"
+	testImplementation 'io.mockk:mockk:1.9.3'
+	testImplementation 'org.skyscreamer:jsonassert:1.5.0'
 	testImplementation 'khttp:khttp:0.1.0'
 
-	kaptTest 'com.google.dagger:dagger-compiler:2.22.1'
+	kaptTest "com.google.dagger:dagger-compiler:$daggerVersion"
 }
 
 jar {