[geary] README.md: Update Matrix channel to point to GNOME's server

[Michael Gratton <mjog src gnome org>]

commit 9064d3538996b6a8491429927bf1ed0de658d58d
Author: Michael Gratton <mike vee net>
Date:   Wed Aug 19 11:18:08 2020 +1000

    README.md: Update Matrix channel to point to GNOME's server

 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README.md b/README.md
index cbcb5ae29..d99cd8aa9 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,7 @@ Getting in Touch
 
  * Geary wiki: https://wiki.gnome.org/Apps/Geary
  * Support and discussion: See the `geary` tag on [GNOME 
Discourse](https://discourse.gnome.org/tags/c/applications/7/geary)
- * Matrix channel: [#_gimpnet_#geary:gnome.org](https://riot.im/app/#/room/#_gimpnet_#geary:gnome.org)
+ * Matrix channel: [#geary:gnome.org](https://gnome.element.io/#/room/#geary:gnome.org)
 
 **Code Of Conduct**