Fix --rcv-timeout manual text (#1642)

* Fix --rcv-timeout manual text

Correct the default value in ms from `12000` to `120000`.

Source of truth: https://github.com/esnet/iperf/blob/master/src/iperf_api.h#L71

* Fix --rcv-timeout manual text

Author: notgba

docs/invoking.rst

@@ -194,7 +194,7 @@ the executable.
           --rcv-timeout #
                  set idle timeout for receiving data  during  active  tests.  The
                  receiver will halt a test if no data is received from the sender
-                 for this number of ms (default to 12000 ms, or 2 minutes).
+                 for this number of ms (default to 120000 ms, or 2 minutes).
    
           --snd-timeout #
                  set timeout for unacknowledged TCP data (on both test  and  con-

src/iperf3.1

@@ -183,7 +183,7 @@ follow the \fB--timestamps\fR option with no whitespace intervening.
 .BR --rcv-timeout " \fI#\fR"
 set idle timeout for receiving data during active tests. The receiver
 will halt a test if no data is received from the sender for this
-number of ms (default to 12000 ms, or 2 minutes).
+number of ms (default to 120000 ms, or 2 minutes).
 .TP
 .BR --snd-timeout " \fI#\fR"
 set timeout for unacknowledged TCP data (on both test and control