bump up jacoco to the latest (0.8.2)
bump up jacoco to the latest (0.8.2)

`append` option will be removed from gradle 5. And its default is `true`,
so we can simply remove this config from gradle file.

spotbugs/spotbugs,spotbugs/spotbugs,spotbugs/spotbugs,spotbugs/spotbugs,spotbugs/spotbugs