specs: fix order-dependant tests in spec/models/gestionnaire_spec.rb
specs: fix order-dependant tests in spec/models/gestionnaire_spec.rb

Test run that would fail randomly before:

```
bin/rspec --seed 10002 spec/models/dossier_spec.rb spec/models/gestionnaire_spec.rb
```

sgmap/tps,sgmap/tps,sgmap/tps