[geary/mjog/959-unloc-button] ui/composer-headerbar.ui: Fix label not being marked as translatable

[Michael Gratton <mjog src gnome org>]

commit 5ab4838a77f9120c311dfe713d12ba59abf9808b
Author: Michael Gratton <mike vee net>
Date:   Tue Sep 1 21:38:32 2020 +1000

    ui/composer-headerbar.ui: Fix label not being marked as translatable
    
    Fixes #959

 ui/composer-headerbar.ui | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/ui/composer-headerbar.ui b/ui/composer-headerbar.ui
index 2e2501d09..13db768a6 100644
--- a/ui/composer-headerbar.ui
+++ b/ui/composer-headerbar.ui
@@ -58,7 +58,7 @@
       <object class="GtkButton">
         <property name="visible">True</property>
         <property name="can_focus">True</property>
-        <property name="label">Cancel</property>
+        <property name="label" translatable="yes">Cancel</property>
         <property name="action_name">cmh.composer-close</property>
       </object>
     </child>