Upgrade gradle-lombok plugin to 4.0.0 (#517)

Author: tokuhirom

build.gradle

@@ -34,7 +34,7 @@ buildscript {
         classpath 'com.github.ben-manes:gradle-versions-plugin:0.27.0'
         classpath 'com.puppycrawl.tools:checkstyle:8.32'
         classpath 'gradle.plugin.com.github.spotbugs:spotbugs-gradle-plugin:2.0.0'
-        classpath 'io.franzbecker:gradle-lombok:3.3.0'
+        classpath 'io.franzbecker:gradle-lombok:4.0.0'
         classpath 'io.spring.gradle:dependency-management-plugin:1.0.9.RELEASE'
         classpath "org.springframework.boot:spring-boot-gradle-plugin:$spring_boot_version"
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"