crypto/rsa: remove obsolete TODO.

(PSS support is complete.)

Thanks to Frithjof Schulze for noting this.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/10871046

src/pkg/crypto/rsa/rsa.go

@@ -5,8 +5,6 @@
 // Package rsa implements RSA encryption as specified in PKCS#1.
 package rsa
 
-// TODO(agl): Add support for PSS padding.
-
 import (
 	"crypto/rand"
 	"crypto/subtle"