Documentation: netdev: fix dead link in ax25.rst

http://linux-ax25.org has been down for nearly a year. Its official
replacement is https://linux-ax25.in-berlin.de.

Update the documentation to point there instead. And acknowledge that
while the linux-hams list isn't entirely dead, it isn't what most would
call 'active'. Remove that word.

Link: https://marc.info/?m=166792551600315
Signed-off-by: Peter Lafreniere <peter@n8pjl.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: n8pjl

Documentation/networking/ax25.rst

@@ -7,9 +7,9 @@ AX.25
 To use the amateur radio protocols within Linux you will need to get a
 suitable copy of the AX.25 Utilities. More detailed information about
 AX.25, NET/ROM and ROSE, associated programs and utilities can be
-found on http://www.linux-ax25.org.
+found on https://linux-ax25.in-berlin.de.
 
-There is an active mailing list for discussing Linux amateur radio matters
+There is a mailing list for discussing Linux amateur radio matters
 called linux-hams@vger.kernel.org. To subscribe to it, send a message to
 majordomo@vger.kernel.org with the words "subscribe linux-hams" in the body
 of the message, the subject field is ignored.  You don't need to be