Add test tolerance

Covers change from use of FastMath in Commons Math3 to the Java Math
class.

Author: aherbert

gdsc-smlm/src/test/java/uk/ac/sussex/gdsc/smlm/math3/distribution/fitting/MultivariateGaussianMixtureExpectationMaximizationTest.java

@@ -131,7 +131,8 @@ void canCreateMultivariateGaussianDistribution() {
     final MultivariateNormalDistribution expDist =
         new MultivariateNormalDistribution(means, covariances);
     for (final double[] x : data) {
-      Assertions.assertEquals(expDist.density(x), dist.density(x));
+      final double e = expDist.density(x);
+      Assertions.assertEquals(e, dist.density(x), Math.ulp(e));
     }
   }