doc: remove file.go from run (fix windows build)

R=golang-dev, r, alex.brainman, r
CC=golang-dev
https://golang.org/cl/5479069

doc/progs/run

@@ -35,7 +35,6 @@ go_tutorial="
 	cat.go 
 	cat_rot13.go 
 	echo.go 
-	file.go
 	helloworld.go 
 	helloworld3.go 
 	print.go