Fix minor typo in doc in replace.h.
Fix minor typo in doc in replace.h.

hemmingway/thrust,h1arshad/thrust,bfurtaw/thrust,rdmenezes/thrust,hemmingway/thrust,Vishwa07/thrust,julianromera/thrust,h1arshad/thrust,google-code-export/thrust,lishi0927/thrust,rdmenezes/thrust,hemmingway/thrust,lishi0927/thrust,levendlee/thrust,h1arshad/thrust,julianromera/thrust,allendaicool/thrust,Vishwa07/thrust,lishi0927/thrust,Vishwa07/thrust,UIKit0/thrust,malenie/thrust,levendlee/thrust,malenie/thrust,malenie/thrust,rdmenezes/thrust,hemmingway/thrust,bfurtaw/thrust,levendlee/thrust,google-code-export/thrust,google-code-export/thrust,Vishwa07/thrust,google-code-export/thrust,rdmenezes/thrust,UIKit0/thrust,UIKit0/thrust,julianromera/thrust,malenie/thrust,bfurtaw/thrust,allendaicool/thrust,UIKit0/thrust,levendlee/thrust,allendaicool/thrust,julianromera/thrust,h1arshad/thrust,lishi0927/thrust,allendaicool/thrust,bfurtaw/thrust