[balsa: 2/16] Update reference for Pine technical notes about folder locking

[Peter Bloomfield <peterb src gnome org>]

commit 3e60b1d0e419fe27fe8973ed22fa56be06112962
Author: Daniel Kahn Gillmor <dkg fifthhorseman net>
Date:   Thu Feb 13 15:42:47 2020 -0500

    Update reference for Pine technical notes about folder locking

 README | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README b/README
index d6d318d1a..52a1f25d1 100644
--- a/README
+++ b/README
@@ -201,7 +201,7 @@ Mailbox locking:
         Balsa uses flock+dotfile for mailbox file locking. It does not
 use fcntl (although it can be enabled) since this locking method is
 very fragile and often not portable (see for example
-http://www.washington.edu/pine/tech-notes/low-level.html#locking).
+https://web.pa.msu.edu/reference/pine-tech-notes/low-level.html#locking).
 
         Make sure that your spool directory has drwxrwxrwt (01777) access
 privileges. Presently, dotfile locking requires this unconditionally