Redundant asignation on Sequences Matrix = operator

[Vicfero]

https://github.com/scapella/trimal/blob/b240b070f0c9651761361bb3d55bd0e3c328558a/source/sequencesMatrix.cpp#L92

should be

matrix[i][j] = matrix[j][i];

[scapella]

Obviously it seems like a bug but ... shouldn't it be?

matrix[i][j] = old.matrix[i][j];