Fix crash with numpy 2.0

Replace `numpy.cast` with `numpy.asarray` which seems to be available
in `numpy` 1.X as well.

Closes: singularity#346

Author: nthykier

singularity/code/buyable.py

@@ -194,7 +194,8 @@ def calculate_work(self, cash_available, cpu_available, time=0):
         # And apply it.
         was_complete = self.cost_paid
         cost_paid = numpy.maximum(
-            numpy.cast[int64](numpy.round(raw_paid)), was_complete
+            numpy.asarray(numpy.round(raw_paid), dtype=int64),
+            was_complete,
         )
         spent = cost_paid - was_complete
         return spent, cost_paid