I have that line also in mijn settings.gradle.
My Gradle version is 5.2.1… which is low and strange, because it is the one installed by IntelliJ during loading of project.
So a pretty basic error.
However I was thrown off guard, because I use Gradle 5.6 in other projects, but I tried a simple new MPP project from the IntelliJ templates and it installed 5.2.1?
My IntelliJ build info is:
IntelliJ IDEA 2019.2.3 (Ultimate Edition)
Build #IU-192.6817.14, built on September 24, 2019
Licensed to [...]
Subscription is active until April 23, 2020
Runtime version: 11.0.4+10-b304.69 x86_64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.14.6
Tried with the latest Kotlin plugin EAP: Kotlin 1.3.60 Early Access Preview. It uses Gradle 5.5.1 (at least in Multiplatform Library template). You’re welcome to try too.