proto: s/Printf/Print/ where there's no format verb

proto/text.go

@@ -154,7 +154,7 @@ func (w *textWriter) indent() { w.ind++ }
 
 func (w *textWriter) unindent() {
 	if w.ind == 0 {
-		log.Printf("proto: textWriter unindented too far")
+		log.Print("proto: textWriter unindented too far")
 		return
 	}
 	w.ind--