Typo followup

Looking at 3ec9b582 I realized that this single sentence was packed
with mistakes: allocation should also have been plural and it wasn't the
third but fourth allocation that would fail (and of course the frist
typo).

include/tbl/cli_cmds.h

@@ -330,8 +330,9 @@ CLI_CMD(DEBUG_REQPOOLFAIL,
 	"debug.reqpool.fail",
 	"Schedule req-pool failures.",
 	"The argument is read L-R and 'f' means fail:\n\n"
-	"\tparam.set debug.reqpoolfail F__F\n\n"
-	"Means that the first and the third attempted allocation will fail",
+	"\tparam.set debug.reqpoolfail F__F_F\n\n"
+	"In the example above the first, fourth and sixth attempted\n"
+	"allocations will fail.",
 	1, 1
 )
 CLI_CMD(DEBUG_XID,