[shotwell] Update README.md

[Jens Georg <jensgeorg src gnome org>]

commit fa8b788d5d3ab84f995b3b6c66d05be72095663d
Author: Jens Georg <mail jensge org>
Date:   Sat Jul 30 00:09:10 2022 +0200

    Update README.md
    
    Drop reference to the now defunct mailing list, add link to Discourse
    
    Fixes #4985

 README.md | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/README.md b/README.md
index 707b798a..cdfafe1e 100644
--- a/README.md
+++ b/README.md
@@ -43,8 +43,9 @@ Shotwell project page:      https://wiki.gnome.org/Apps/Shotwell
 Shotwell documentation:     http://shotwell-project.org/doc/html/
 GNOME Gitlab Project:       https://gitlab.gnome.org/GNOME/shotwell
 
-We also encourage you to join the Shotwell mailing list. See
-https://mail.gnome.org/mailman/listinfo/shotwell-list for how to subscribe
-to the mailing list.
+The place for discussions with other users of Shotwell is GNOME's discourse,
+using the Application category and the tag "shotwell":
+
+https://discourse.gnome.org/tag/shotwell
 
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