Update Mockito to hopefully fix OpenJDK 14 problems

Author: tschuchortdev

build.gradle

@@ -48,7 +48,7 @@ dependencies {
     kapt "com.google.auto.service:auto-service:1.0-rc2"
 
     testImplementation "org.assertj:assertj-core:3.11.1"
-    testImplementation "org.mockito:mockito-core:3.1.0"
+    testImplementation "org.mockito:mockito-core:3.2.4"
     testImplementation "com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0"
 
     testImplementation 'com.squareup:kotlinpoet:1.4.0'