QEE: Prescale Hlt2QEE_SexaquarkProtonToLambda0Kp_DDdDecision

FYI @lugrazet @isanders @wmorren @pkoppenb @mvesteri

In recent tests the Hlt2QEE_SexaquarkProtonToLambda0Kp_DDd line was observed to be taking > 100 MB/s to disk on real data, which is much higher than anticipated based on MC.

As discussed here with the proponents I've applied a 0.1 prescale to remedy this.

Can be merged whenever the maintainers see fit.