doc: describe tcl port consistently.

One place described the tcl port as 5555, which was changed in 163bd86
Reported on IRC.

Change-Id: If740a29443793d6a4d4f8c9db54f0fc8344a6c1c
Signed-off-by: Karl Palsson <[email protected]>
Reviewed-on: https://review.openocd.org/c/openocd/+/7385
Tested-by: jenkins
Reviewed-by: Antonio Borneo <[email protected]>

Author: karlp

doc/openocd.texi

@@ -8523,7 +8523,7 @@ command. All output is relayed through the GDB session.
 
 @item @b{Machine Interface}
 The Tcl interface's intent is to be a machine interface. The default Tcl
-port is 5555.
+port is 6666.
 @end itemize