Fix breaking change from lombok

[hongji3354]

According to issue #110, pom.xml is updated to version 1.18.16 of lombok, but not to build.grade.

So I updated it as below.

ext {
    mapstructVersion = "1.4.1.Final"
    lombokVersion = "1.18.16"
    lombokMapstructBindingVersion = "0.2.0"
}

sourceCompatibility = JavaVersion.VERSION_1_8

dependencies {
    implementation "org.mapstruct:mapstruct:${mapstructVersion}", "org.projectlombok:lombok:${lombokVersion}"
    testImplementation 'junit:junit:4.13.1'
    annotationProcessor "org.mapstruct:mapstruct-processor:${mapstructVersion}", "org.projectlombok:lombok:${lombokVersion}", "org.projectlombok:lombok-mapstruct-binding:${lombokMapstructBindingVersion}"
}

[filiphr]

Thanks for the fix @hongji3354, I forgot about the gradle build.