ACPI: OSI: Remove Linux-HPI-Hybrid-Graphics _OSI string

This string was introduced because drivers for NVIDIA hardware
didn't handle mux control properly.

This was fixed by commit 8e55f99c ("drm/i915: Invoke another _DSM
to enable MUX on HP Workstation laptops"), so vendors shouldn't be
using this string to modify ASL any more.

Suggested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>