drm/vkms: drop "Rotation" TODO

Now that VKMS supports all values of rotation and reflection, drop the
"Rotation" task from the TODO list.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230418130525.128733-7-mcanal@igalia.com