Revert "ssh: add support for banners"

This reverts commit ed5229da99.

Reason for revert: missing language tag in banner message breaks auth against other implementations.

Change-Id: I18ac5b3fe3b4693688b82ff4b0db02dab739c45b
Reviewed-on: https://go-review.googlesource.com/72381
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ssh/messages.go

@@ -23,6 +23,10 @@ const (
 	msgUnimplemented = 3
 	msgDebug         = 4
 	msgNewKeys       = 21
+
+	// Standard authentication messages
+	msgUserAuthSuccess = 52
+	msgUserAuthBanner  = 53
 )
 
 // SSH messages:
@@ -133,16 +137,6 @@ type userAuthFailureMsg struct {
 	PartialSuccess bool
 }
 
-// See RFC 4252, section 5.1
-const msgUserAuthSuccess = 52
-
-// See RFC 4252, section 5.4
-const msgUserAuthBanner = 53
-
-type userAuthBannerMsg struct {
-	Message string `sshtype:"53"`
-}
-
 // See RFC 4256, section 3.2
 const msgUserAuthInfoRequest = 60
 const msgUserAuthInfoResponse = 61