Fix D02hhpi0 lines

The lines were extremely subperformant due to a cut to the DOCACHI2 variable in the D*+->D0pi builder (this is also evincible from !2414 (closed)). The D*+->D0pi builder has been substituted with the same used for the D0->hh decays defined in taggers.py.

Rates before and after:

Hlt2 line	rate before [kHz]	rate after [kHz]
Hlt2Charm_DstpToD0Pip_D0ToKmKpPi0_MDecision	0.0 +/- 0.0	0.0 +/- 0.0
Hlt2Charm_DstpToD0Pip_D0ToKmKpPi0_RDecision	0.0 +/- 0.0	0.20022 +/- 0.1155
Hlt2Charm_DstpToD0Pip_D0ToKmPipPi0_MDecision	0.0 +/- 0.0	0.0 +/- 0.0
Hlt2Charm_DstpToD0Pip_D0ToKmPipPi0_RDecision	0.06674 +/- 0.0667	1.20136 +/- 0.2829
Hlt2Charm_DstpToD0Pip_D0ToPimPipPi0_MDecision	0.0 +/- 0.0	0.33371 +/- 0.1492
Hlt2Charm_DstpToD0Pip_D0ToPimPipPi0_RDecision	0.06674 +/- 0.0667	1.60181 +/- 0.3267