fix(api): stacker home routine should open latch before moving z up (#18997)

# Overview
This fixes a bug surfaced in QA where a labware can get stuck in the
latch and prevents the stacker shuttle from homing.

Author: ahiuchingau

api/src/opentrons/hardware_control/modules/flex_stacker.py

@@ -616,6 +616,8 @@ async def home_all(self, ignore_latch: bool = False) -> None:
         if not ignore_latch:
             if self.limit_switch_status[StackerAxis.Z] == StackerAxisState.UNKNOWN:
                 if self.latch_state == LatchState.OPENED:
+                    # let's make sure the latch is opened all the way before homging the Z
+                    await self.open_latch()
                     # self.latch_state is OPENED, so we need to home Z in the EXTEND direction
                     await self.home_axis(StackerAxis.Z, Direction.EXTEND)
             await self.close_latch()