crypto/rsa: remove unused variable y

Change-Id: I70beb844cd6928dbfbfd8de365e0cb708e54f71e
Reviewed-on: https://go-review.googlesource.com/28496
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/rsa/rsa.go

@@ -268,9 +268,8 @@ NextSetOfPrimes:
 
 		g := new(big.Int)
 		priv.D = new(big.Int)
-		y := new(big.Int)
 		e := big.NewInt(int64(priv.E))
-		g.GCD(priv.D, y, e, totient)
+		g.GCD(priv.D, nil, e, totient)
 
 		if g.Cmp(bigOne) == 0 {
 			if priv.D.Sign() < 0 {