Lower Manhattan’s 9/11 Tribute Museum — a nearly 30,000-square-foot space located three blocks from the World Trade Center site — will shut its doors Wednesday afternoon, just weeks shy of the 21st anniversary of the terror attacks. The Greenwich Street museum, which opened in 2006 nearby on Liberty Street, has struggled to stay afloat since the 2020 onset of the COVID-19 pandemic. “Two-thirds of our income revenue annually comes from our earned income from admissions,” Jennifer Adams-Webb, co-founder of the museum and the CEO of the September 11th Families’ Association, told The Post. “We were completely closed for six months...