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.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>