ssh: fix typo in error message

Fix typo in error message when keyboard-interactive auth not supported by server and client requests it

Change-Id: Iedb72625852f03552481d85cce2119765cfba320
GitHub-Last-Rev: ee47092daf8c40fe3e0e166e7370556819457af6
GitHub-Pull-Request: golang/crypto#59
Reviewed-on: https://go-review.googlesource.com/c/141658
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

ssh/server.go

@@ -404,7 +404,7 @@ userAuthLoop:
 			perms, authErr = config.PasswordCallback(s, password)
 		case "keyboard-interactive":
 			if config.KeyboardInteractiveCallback == nil {
-				authErr = errors.New("ssh: keyboard-interactive auth not configubred")
+				authErr = errors.New("ssh: keyboard-interactive auth not configured")
 				break
 			}