ENH: Update DTIPrep from revision 6d9fdc556d5b20be7ab6bd141bf7a187ab7933a7 to 44f7302015bbecc1890c1cb975a95fae9da2f893

https://www.github.com/NIRALUser/DTIPrep/compare/6d9fdc556d5b20be7ab6bd141bf7a187ab7933a7%E2%80%A644f7302015bbecc1890c1cb975a95fae9da2f893