go.tools/cmd/vet: enable test (fix build)

R=r
TBR=r
CC=golang-dev
https://golang.org/cl/12482043

cmd/vet/testdata/print.go

@@ -121,7 +121,7 @@ func PrintfTests() {
 	fmt.Printf("%t", stringerarrayv)           // ERROR "arg stringerarrayv for printf verb %t of wrong type"
 	fmt.Printf("%t", notstringerarrayv)        // ERROR "arg notstringerarrayv for printf verb %t of wrong type"
 	fmt.Printf("%q", notstringerarrayv)        // ERROR "arg notstringerarrayv for printf verb %q of wrong type"
-	fmt.Printf("%s", nonemptyinterface)        // NOTERROR "for printf verb %s of wrong type" (Disabled temporarily because of bug in IsAssignableTo)
+	fmt.Printf("%s", nonemptyinterface)        // ERROR "for printf verb %s of wrong type" (Disabled temporarily because of bug in IsAssignableTo)
 	fmt.Printf("%.*s %d %g", 3, "hi", 23, 'x') // ERROR "arg 'x' for printf verb %g of wrong type"
 	fmt.Println()                              // not an error
 	fmt.Println("%s", "hi")                    // ERROR "possible formatting directive in Println call"