Remove manual prefix generation with the next Firedrake release.

[JHopeCollins]

asQ/utils/serial/miniapp.py

Lines 37 to 40 in 56bad0b

	# mismatch in firedrake 2025.10.2 and petsctools version
	# means that the default prefix for NLVS is "petsctools_%d"
	# rather than "firedrake_%d", so we manually make a count.
	options_prefix = options_prefix or f"asq_serial_{next(self._count)}"