For more than 11 years, a core group of about 100 die-hard parishioners of St. Frances X. Cabrini Church have kept their beloved parish open by maintaining an around-the-clock vigil in a peaceful protest of a decision by the Roman Catholic Archdiocese of Boston to close it. On Sunday, the parishioners' efforts will end and they will vacate the Scituate church many of them have attended for decades.