The Democratic mayor of a Georgia city was heckled and encouraged to resign during a news conference Wednesday morning, a week after a college student was murdered on the campus of the University of Georgia — allegedly by a Venezuelan national who was in the country illegally. Athens-Clarke County Mayor Kelly Girtz told residents of the area that his community is not a sanctuary city as people have begun to blame the horrific murder of nursing student Laken Riley on him and others. Girtz spoke at a police podium Tuesday where he was met with backlash from vocal protesters, WAGA-TV reported. T…