Fix dead URLs to ftp.kernel.org

URLs to ftp.kernel.org are still exist though the service is closed [0].
This commit fixes the URLs to use www.kernel.org instead.

[0] https://www.kernel.org/shutting-down-ftp-services.html

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/fs/autofs4/Kconfig b/fs/autofs4/Kconfig
index 1204d63..44727bf 100644
--- a/fs/autofs4/Kconfig
+++ b/fs/autofs4/Kconfig
@@ -7,7 +7,7 @@
 	  automounter (amd), which is a pure user space daemon.
 
 	  To use the automounter you need the user-space tools from
-	  <ftp://ftp.kernel.org/pub/linux/daemons/autofs/v4/>; you also
+	  <https://www.kernel.org/pub/linux/daemons/autofs/v4/>; you also
 	  want to answer Y to "NFS file system support", below.
 
 	  To compile this support as a module, choose M here: the module will be