Disabled external gits

cs440-acg/ext/eigen/doc/snippets/SelfAdjointEigenSolver_operatorSqrt.cpp

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+MatrixXd X = MatrixXd::Random(4,4);
+MatrixXd A = X * X.transpose();
+cout << "Here is a random positive-definite matrix, A:" << endl << A << endl << endl;
+
+SelfAdjointEigenSolver<MatrixXd> es(A);
+MatrixXd sqrtA = es.operatorSqrt();
+cout << "The square root of A is: " << endl << sqrtA << endl;
+cout << "If we square this, we get: " << endl << sqrtA*sqrtA << endl;