Update ISF_Services TruthSvc_test to match current behaviour in master

The `parentParticle` method is called once less often in ~master than
in ~"21.0". This will change once the other updates from ~"21.0" are swept
into ~master.

Simulation/ISF/ISF_Core/ISF_Services/test/TruthSvc_test.cxx

@@ -348,8 +348,7 @@ namespace ISFTesting {
       .WillOnce(::testing::Return(inParticle3->barcode()))
       .WillOnce(::testing::Return(inParticle3->barcode()));
     EXPECT_CALL(ti, parentParticle())
-      .Times(2)
-      .WillOnce(::testing::Return(inParticle3))
+      .Times(1)
       .WillOnce(::testing::Return(inParticle3));
     EXPECT_CALL(ti, parentParticleAfterIncident(1010003))
       .Times(1)
@@ -580,8 +579,7 @@ namespace ISFTesting {
       .WillOnce(::testing::Return(inParticle3->barcode()))
       .WillOnce(::testing::Return(inParticle3->barcode()));
     EXPECT_CALL(ti, parentParticle())
-      .Times(2)
-      .WillOnce(::testing::Return(inParticle3))
+      .Times(1)
       .WillOnce(::testing::Return(inParticle3));
     EXPECT_CALL(ti, parentParticleAfterIncident(1010003))
       .Times(1)