libcontainer/sync: Drop procConsole transaction from comments

These were added in 244c9fc (*: console rewrite, 2016-06-04, opencontainers#1018)
alongside procConsole and the associated handling.  procConsole and
that handling were removed in 00a0ecf (Add separate console socket,
2017-03-02, opencontainers#1356), but 00a0ecf missed this comment.

Signed-off-by: W. Trevor King <wking@tremily.us>

libcontainer/sync.go

@@ -19,11 +19,6 @@ type syncType string
 // procHooks   --> [run hooks]
 //             <-- procResume
 //
-// procConsole -->
-//             <-- procConsoleReq
-//  [send(fd)] --> [recv(fd)]
-//             <-- procConsoleAck
-//
 // procReady   --> [final setup]
 //             <-- procRun
 const (