There was a celebration Friday at Conwell-Egan High School in Fairless Hills, Bucks County.   The Archdiocese of Philadelphia will keep it open next year in spite of a blue ribbon commission recommendation that it be closed.   Three other parochial high schools that were also slated for closure will remain open too.   They are Saint Hubert Catholic High School for Girls in Northeast Philadelphia and West Philadelphia Catholic as well as Monsignor Bonner/Archbishop Prendergast in Drexel Hill, Delaware County.   Philadelphia Archdiocese officials say they are taking the high schools off the closure list because of fundraising efforts on their behalf.   Parents, students and friends of Conwell-Egan have collected about $3,000,000 in donations to keep it open.