net/tcp: Expand goo.gl link

The goo.gl URL shortener is deprecated and is due to stop
expanding existing links in 2025.

Expand the link in Kconfig.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240729205337.48058-1-linux@treblig.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/Kconfig

@@ -661,7 +661,8 @@ config TCP_CONG_CDG
 
 	  For further details see:
 	    D.A. Hayes and G. Armitage. "Revisiting TCP congestion control using
-	    delay gradients." In Networking 2011. Preprint: http://goo.gl/No3vdg
+	    delay gradients." In Networking 2011. Preprint:
+	    http://caia.swin.edu.au/cv/dahayes/content/networking2011-cdg-preprint.pdf
 
 config TCP_CONG_BBR
 	tristate "BBR TCP"