Allocate less memory in AddrForKey

This backports the microoptimization fix initially introduced in [1].

[1]: yggdrasil-network/yggdrasil-go#801

crypto.go

@@ -28,7 +28,7 @@ func AddrForKey(key ed25519.PublicKey) *address.Address {
 		buf[idx] = ^buf[idx]
 	}
 	var addr address.Address
-	var temp = make([]byte, 0, 128)
+	var temp = make([]byte, 0, 32)
 	done := false
 	ones := byte(0)
 	bits := byte(0)