Prescale SpruceBandQ_BdToEtacKpPim_EtacToHHHH line for sprucing rate tuning

This MR is to react for #549 (closed) and https://gitlab.cern.ch/lhcb-dpa/project/-/issues/243 .

The expected rate of mengzhen_Prescale_SpruceBandQ_BdToEtacKpPim_EtacToHHHH is too high in the centralized test. The rate should be reduced with a factor of a few percents. Prescale it for now. (May tighten the selection and release the prescale in the future.)

Hlt/Hlt2Conf/python/Hlt2Conf/lines/bandq/spruce_bandq.py

@@ -113,7 +113,7 @@ def LbToEtacPpKm_EtacToHHHH_sprucing_line(
 @register_line_builder(sprucing_lines)
 @configurable
 def BdToEtacKpPim_EtacToHHHH_sprucing_line(
-        name='SpruceBandQ_BdToEtacKpPim_EtacToHHHH', prescale=1):
+        name='SpruceBandQ_BdToEtacKpPim_EtacToHHHH', prescale=0.8):
     """B0 -> Etac K+ pi- line"""
     line_alg = b_to_etacX_lines.make_BdToEtacKpPim_EtacToHHHH()
     return SpruceLine(