CAPE CANAVERAL, Fla. — NASA has replaced an astronaut assigned to Boeing’s first launch with a crew. Astronaut Eric Boe was pulled Tuesday from the upcoming test flight for unspecified medical reasons, after more than three years of training. Taking his seat will be Mike Fincke, a former space station commander. Boeing plans to launch its first Starliner capsule without a crew this spring, followed by a launch with astronauts this summer to the International Space Station. SpaceX — NASA’s other commercial crew partner — could launch its Dragon capsule, minus a crew, next month.