[geary/geary-0.12] Bump flatpak runtime to 3.28.

[Michael Gratton <mjog src gnome org>]

commit 77e435e3c8c56c375f2b20873ae64ee7831d21aa
Author: Michael James Gratton <mike vee net>
Date:   Wed Apr 11 14:45:42 2018 +1000

    Bump flatpak runtime to 3.28.

 org.gnome.Geary.json |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/org.gnome.Geary.json b/org.gnome.Geary.json
index 5605138..1656a76 100644
--- a/org.gnome.Geary.json
+++ b/org.gnome.Geary.json
@@ -2,7 +2,7 @@
 {
     "app-id": "org.gnome.Geary",
     "runtime": "org.gnome.Platform",
-    "runtime-version": "3.26",
+    "runtime-version": "3.28",
     "sdk": "org.gnome.Sdk",
     "command": "geary",
     "finish-args": [