internal/socks: fix typo in comment

Follow-up fix for CL 115237 which fixed the generated file.

Change-Id: I17881ce4ad1fc8f7d74b2b78e515d5d5430ad451
Reviewed-on: https://go-review.googlesource.com/115275Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

internal/socks/socks.go

@@ -75,7 +75,7 @@ const (
 
 	AuthMethodNotRequired         AuthMethod = 0x00 // no authentication required
 	AuthMethodUsernamePassword    AuthMethod = 0x02 // use username/password
-	AuthMethodNoAcceptableMethods AuthMethod = 0xff // no acceptable authetication methods
+	AuthMethodNoAcceptableMethods AuthMethod = 0xff // no acceptable authentication methods
 
 	StatusSucceeded Reply = 0x00
 )