Use newer assertj version

[comdotlinux]

We have to exclude assertj from this dependency and add our own to take the newer version, I bet others also have to do the same. This would at least to some extent help with that.

so

testImplementation("net.wuerl.kotlin:assertj-core-kotlin:0.2.1") {
    exclude(group = "org.assertj", module = "assertj-core") // otherwise, this is forced to be 3.7.0
}

would become

testImplementation("net.wuerl.kotlin:assertj-core-kotlin:0.2.1")