Enable export of transient probability computation for MTBDD engine.

Was already enabled for steady-state probabilities in 3cb4f42d,
following addition of no-sparse printing for MTBDD vectors.
Not sure why this was not enabled too.

prism/src/prism/Prism.java

@@ -3607,8 +3607,6 @@ public class Prism extends PrismComponent implements PrismSettingsListener
 			throw new PrismException("Steady-state probabilities only computed for DTMCs/CTMCs");
 		if (time < 0)
 			throw new PrismException("Cannot compute transient probabilities for negative time value");
-		if (fileOut != null && getEngine() == MTBDD)
-			throw new PrismException("Transient probability export only supported for sparse/hybrid engines");
 		if (exportType == EXPORT_MRMC)
 			exportType = EXPORT_PLAIN; // no specific states format for MRMC
 		if (exportType == EXPORT_ROWS)
@@ -3704,8 +3702,6 @@ public class Prism extends PrismComponent implements PrismSettingsListener
 		// Do some checks
 		if (!(currentModelType == ModelType.CTMC || currentModelType == ModelType.DTMC))
 			throw new PrismException("Steady-state probabilities only computed for DTMCs/CTMCs");
-		if (fileOut != null && getEngine() == MTBDD)
-			throw new PrismException("Transient probability export only supported for sparse/hybrid engines");
 		if (exportType == EXPORT_MRMC)
 			exportType = EXPORT_PLAIN; // no specific states format for MRMC
 		if (exportType == EXPORT_ROWS)