Former Weather Underground radical Kathy Boudin — who spent 22 years in prison for an armored-car robbery that killed two cops and a Brinks guard — now holds a prestigious adjunct professorship at Columbia University’s School of Social Work, The Post has learned. Boudin, 69, this year won another academic laurel — being named the Sheinberg Scholar-in-Residence at NYU Law School, where last month she gave a lecture on “the politics of parole and re-entry.” Of the hundreds of students Boudin has taught, Yoshioka said, just three have expressed qualms about her criminal background,