Use minimal job configuration for test-read-genfsr
!1068 (merged) added a test to ensure that the genfsr written in the output ntuple file is correct, but to do it we configure a full DaVinci job.
The test relies on the assumption that we can pretend that an n-tuple file can be read as if it was a normal data file in Gaudi. This assumption does not hold when we use IOAlg (from LHCb!2993 (merged)).
OTOH, the test does not need to configure a full DaVinci job via lbexec: it's enoughto configure a minimal Gaudi job that is able to load the FSR and dump it in XML.
This MR ports to 2024-patches the change I added !1075 (merged) to make the test pass.