vfio/pci: Drop debug commentary from x-device-dirty-page-tracking

vfio/pci: Drop debug commentary from x-device-dirty-page-tracking

The intent behind the x-device-dirty-page-tracking option is twofold:

1) development/testing in the presence of VFs with VF dirty page tracking

2) deliberately choosing platform dirty tracker over the VF one.

Item 2) scenario is useful when VF dirty tracker is not as fast as
IOMMU, or there's some limitations around it (e.g. number of them is
limited; aggregated address space under tracking is limited),
efficiency/scalability (e.g. 1 pagetable in IOMMU dirty tracker to scan
vs N VFs) or just troubleshooting. Given item 2 it is not restricted to
debugging, hence drop the debug parenthesis from the option description.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250311174807.79825-1-joao.m.martins@oracle.com
[ clg: Fixed subject spelling ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>