The parameter's name is timeout_linger

There are two timeout names where `timeout` is the prefix:

- timeout_linger
- timeout_idle

If it were up to me, they'd be called the other way around and according
to the documentation:

> `session_linger` has been renamed to `timeout_linger

If it were up to me, it would have been renamed to a self-describing
`session_linger_timeout` (wink wink, nudge nudge).

Typo spotted by scn.

include/tbl/vsc_f_main.h

@@ -390,7 +390,7 @@ VSC_F(sess_readahead,		uint64_t, 1, 'c', 'i', info,
 )
 VSC_F(sess_herd,		uint64_t, 1, 'c', 'i', diag,
     "Session herd",
-	"Number of times the linger_timeout triggered"
+	"Number of times the timeout_linger triggered"
 )
 
 #define SESS_CLOSE_ERR0 "OK  "