tauRec: fix standalone EMTopo script

Hello,

This MR is just fixing a small issue in a AOD file name.
The EMTopo ART test (https://gitlab.cern.ch/atlas/athena/-/blob/master/Reconstruction/tauRec/test/test_tau_standalone_EMTopo_serial.sh) that uses the standalone EMTopo-seeded reconstruction expects `EMTopo_AOD.pool.root`.

Cheers,
Bertrand