[HL-Batch] Remove headless parallel simulation

Allow to have same batch parallel simulations as in gui
+ Function never check by the 'classical' headless mode (with XML files)

msi.gama.core/src/msi/gama/kernel/simulation/SimulationPopulation.java

@@ -47,7 +47,6 @@ public SimulationPopulation(final ExperimentAgent agent, final ISpecies species)
 	}
 
 	public int getMaxNumberOfConcurrentSimulations() {
-		if (getHost().getSpecies().isHeadless()) return 1;
 		return GamaExecutorService.getParallelism(getHost().getScope(), getSpecies().getConcurrency(),
 				Caller.SIMULATION);
 	}