tcp: fix tcp_rmem documentation

tcp_rmem[1] has been changed to 131072, we should update the documentation
to reflect this.

Fixes: a337531b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: NZhibin Liu <zhibinliu@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.rst

@@ -630,16 +630,15 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
 
 	default: initial size of receive buffer used by TCP sockets.
 	This value overrides net.core.rmem_default used by other protocols.
-	Default: 87380 bytes. This value results in window of 65535 with
-	default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
-	less for default tcp_app_win. See below about these variables.
+	Default: 131072 bytes.
+	This value results in initial window of 65535.
 
 	max: maximal size of receive buffer allowed for automatically
 	selected receiver buffers for TCP socket. This value does not override
 	net.core.rmem_max.  Calling setsockopt() with SO_RCVBUF disables
 	automatic tuning of that socket's receive buffer size, in which
 	case this value is ignored.
-	Default: between 87380B and 6MB, depending on RAM size.
+	Default: between 131072 and 6MB, depending on RAM size.
 
 tcp_sack - BOOLEAN
 	Enable select acknowledgments (SACKS).