[releng] tools/smoketesting/tarball-conversion.config: Add back zenity

[Javier Jardón Cabezas <jjardon src gnome org>]

commit c5da4792b8b0824f13ab8a071c8f0c1d4212214d
Author: Javier Jardón <jjardon gnome org>
Date:   Thu May 10 15:23:29 2018 +0100

    tools/smoketesting/tarball-conversion.config: Add back zenity
    
    This was incorrectly removed in
    commit cd6efde26f0a664c214bb44d695f9e4fe16eb2e0

 tools/smoketesting/tarball-conversion.config |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/tools/smoketesting/tarball-conversion.config b/tools/smoketesting/tarball-conversion.config
index 07ff8ec..2ed9e7b 100644
--- a/tools/smoketesting/tarball-conversion.config
+++ b/tools/smoketesting/tarball-conversion.config
@@ -257,6 +257,7 @@
     <package name="vte"                         set="core"/>
     <package name="yelp-xsl"                    set="core"/>
     <package name="yelp-tools"                  set="core"/>
+    <package name="zenity"                      set="core"/>
 
   </whitelist>
 </conversioninfo>