world: Don't use flatpak's system-helper when running the jhbuild ver…

…sion

This will allow us to test flatpak itself, with separate runtimes from
the real system installation, without password prompts.

This also disables sudo usage during installation, to avoid prompting
for passwords when using jhbuild. Note that this will need to be
overridden for distributions without user namespaces support.

See flatpak/flatpak#367

modulesets/gnome-world.modules

@@ -3234,7 +3234,7 @@
     </dependencies>
   </autotools>
 
-  <autotools id="flatpak" autogenargs="--enable-sudo">
+  <autotools id="flatpak" autogenargs="--disable-sudo --disable-system-helper">
     <branch repo="github.com"
             module="flatpak/flatpak"/>
     <dependencies>