fmt: delete erroneous sentence about return value for Sprint*.
fmt: delete erroneous sentence about return value for Sprint*.

R=rsc
CC=golang-dev
http://codereview.appspot.com/2160041

gnanderson/go,dsriram/golang,dsriram/golang,h8liu/golang,gnanderson/go,ssrl/go,pombredanne/go-deleteme,dsriram/golang,ssrl/go,ssrl/go,apparentlymart/golang,dsriram/golang,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,ssrl/go,dsriram/golang,ssrl/go,gnanderson/go,ssrl/go,apparentlymart/golang,h8liu/golang,gnanderson/go,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,apparentlymart/golang,h8liu/golang,gnanderson/go,tv42/old-go,h8liu/golang,apparentlymart/golang,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,h8liu/golang,tv42/old-go,h8liu/golang,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,h8liu/golang,gnanderson/go,pombredanne/go-deleteme,ssrl/go,pombredanne/go-deleteme