Remove unused ClientStateAuthenticating

Appears to be leftover from the Kerberos code deleted in 2007
(commit dfbe32b5b8).
Nothing left ever set clientState to ClientStateAuthenticating

Skipped over 1 to preserve existing enum numbering.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>

include/dixstruct.h

@@ -57,8 +57,8 @@ extern _X_EXPORT void ReplyNotSwappd (
 		void *		/* pbuf */) _X_NORETURN;
 
 typedef enum {ClientStateInitial,
-	      ClientStateAuthenticating,
-	      ClientStateRunning,
+	      /* 1 is unused now, was ClientStateAuthenticating */
+	      ClientStateRunning = 2,
 	      ClientStateRetained,
 	      ClientStateGone
 } ClientState;