Add Generators/GenInterfaces to the list of packages in AthSimulation

MR !4271 introduced a dependency on `Generators/GenInterfaces` in
the `AthSimulation` release, but missed adding it to the list of
packages to be built as part of the `AthSimulation` release.
This change should fix ATLASSIM-3427.

Projects/AthSimulation/package_filters.txt

@@ -162,6 +162,7 @@
 + External/AtlasPyFwdBwdPorts
 + External/CheckerGccPlugins
 + External/pyAMI
++ Generators/GenInterfaces
 + Generators/GeneratorObjects
 + Generators/GeneratorObjectsAthenaPool
 + Generators/GeneratorObjectsTPCnv