Clean up diagonalized via congruence matrix in RR and CC

When using floating point arithmetic, there's a chance we end up with
small nonzero entries off the diagonal thanks to rounding errors.

Author: d-torrance

M2/Macaulay2/packages/A1BrouwerDegrees/Code/MatrixMethods.m2

@@ -107,6 +107,7 @@ diagonalizeViaCongruence Matrix := Matrix => AnonMut -> (
                 );
             );
         );
+    if instance(k, InexactField) then A = clean(1e-12, A);
     matrix A 
     )