Fix unmerged ComponentAccumulator instance in HGTD_DigitizationConfig.HGTD_DigitizationToolCfg
After !61689 (merged), we see a error about an unmerged ComponentAccumulator
instance in HGTD_DigitizationConfig.HGTD_DigitizationToolCfg
when running pile-up digitization for P2 upgrade samples. (This workflow is not tested in the CI.)