Removed assert(false) that I thought was never called

gtsam/linear/NoiseModel.cpp

@@ -122,8 +122,6 @@ void Gaussian::WhitenInPlace(MatrixColMajor& H) const {
 // General QR, see also special version in Constrained
 SharedDiagonal Gaussian::QR(Matrix& Ab, boost::optional<vector<int>&> firstZeroRows) const {
 
-  assert(false);
-
 	// get size(A) and maxRank
 	// TODO: really no rank problems ?
 	size_t m = Ab.size1(), n = Ab.size2()-1;