Remove documentation of -u flag.

babel.man

@@ -48,13 +48,6 @@ at which scheduled hello packets are sent on idle interfaces.  This
 functonality is experimental, don't use it unless you know what you are
 doing.
 .TP
-.BI \-u " update-interval"
-Specify the interval in seconds at which scheduled routing table dumps are
-made on all interfaces.  The default is either 5 times the wireless hello
-interval, twice the wired hello interval, or 70 seconds, whichever is less.
-Babel uses triggered updates in addition to scheduled updates, so this
-value may be set to a fairly large value.
-.TP
 .BI \-k " priority"
 Specify the priority value used when installing routes into the kernel.
 The default is 0.