bugfix D0->KSππ SL lines

[skip ci] This MR fixes a bug in the selection of D⁰→K⁰ₛππ decays from semileptonic B decays.

When the B→D⁰(→ K⁰ₛππ)µX lines were defined three years ago, a copy-paste error was introduced: the order of the daughter particles in the make_dzeros function was not correctly considered. Selection cuts in this function are applied to combinations of particles 1–2 and 2–3 from the list of daughters. Due to the incorrect ordering, no D⁰→K⁰ₛππ candidates were actually selected.

Interestingly, all other D⁰→K⁰ₛhh decay modes are correctly handled.

The variation in bandwidth is estimated in < 1MB/s

Line	BW [MB/s]
Hlt2Charm_B2D0MumX_D0ToKsPimPip_LL	0.231
Hlt2Charm_B2D0MumX_D0ToKsPimPip_DD	0.057
Hlt2Charm_B2DstpMumX_DstpToD0Pip_D0ToKsPimPip_LL	0.0
Hlt2Charm_B2DstpMumX_DstpToD0Pip_D0ToKsPimPip_DD	0.138