Trivial tidy up of unused import.

Author: ctjoreilly

aima-core/src/test/java/aima/test/core/unit/probability/bayes/approx/GibbsAskTest.java

@@ -6,7 +6,6 @@
 import org.junit.Test;
 
 import aima.core.probability.CategoricalDistribution;
-import aima.core.probability.ProbabilityModel;
 import aima.core.probability.RandomVariable;
 import aima.core.probability.bayes.BayesianNetwork;
 import aima.core.probability.bayes.approx.GibbsAsk;