build: fix mockito compilation errors in tests

[BenjaminAmos]

This pull request fixes a compilation error which causes the unit tests to fail.

Currently CI fails with the following error:

> Task :compileTestJava
/home/jenkins/agent/workspace/sology_Modules_P_PolyWorld_PR-43/src/test/java/org/terasology/polyworld/TinyEnvironment.java:18: error: cannot find symbol
import org.mockito.Matchers;
                  ^
  symbol:   class Matchers
  location: package org.mockito
/home/jenkins/agent/workspace/sology_Modules_P_PolyWorld_PR-43/src/test/java/org/terasology/polyworld/TinyEnvironment.java:78: error: cannot find symbol
        Mockito.when(blockManager.getBlock(Matchers.<BlockUri>any())).thenReturn(air);
                                           ^
  symbol:   variable Matchers
  location: class TinyEnvironment
/home/jenkins/agent/workspace/sology_Modules_P_PolyWorld_PR-43/src/test/java/org/terasology/polyworld/TinyEnvironment.java:79: error: cannot find symbol
        Mockito.when(blockManager.getBlock(Matchers.<String>any())).thenReturn(air);
                                           ^
  symbol:   variable Matchers
  location: class TinyEnvironment

Mockito re-named its Matchers class to ArgumentMatchers. The version of Mockito in use was upgraded with the Java 17 changes.