
Probably a misattribution which instead originated with David Mermin; in "Could Feynman Have Said This?" http://scitation.aip.org/journals/doc/PHTOAD-ft/vol_57/iss_5/10_1.shtml?bypassSSO=1, by N. David Mermin, in Physics Today (May 2004), p. 10, he notes that in an earlier Physics Today (April 1989), p. 9, he had written what appears to be the earliest occurrence of the phrase:
If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be "Shut up and calculate!"
Disputed and/or attributed