Set the non-prompt injection ratio to 2

Change the default injection ratio from 5 to 2 for the non-prompt gap-triggered generators, corresponding to one injected signal event every two generated events.

Author: donglovo

MC/config/PWGDQ/external/generator/generator_pythia8_NonPromptSignals_OO_gaptriggered_dq.C

@@ -19,7 +19,7 @@ class GeneratorPythia8NonPromptInjectedOOGapTriggeredDQ : public o2::eventgen::G
 public:
 
   /// constructor
-  GeneratorPythia8NonPromptInjectedOOGapTriggeredDQ(int inputTriggerRatio = 5)  {
+  GeneratorPythia8NonPromptInjectedOOGapTriggeredDQ(int inputTriggerRatio = 2)  {
 
     mGeneratedEvents = 0;
     mInverseTriggerRatio = inputTriggerRatio;