[media] Documentation/DocBook/media/v4l/subdev-formats.xml: fix a typo

The xref to the v4l2-mbus-pixelcode-yuv8 table gets rendered as "Table
4.22, “YUV Formats”", so use the verb in the third person singular
because it refers to "Table":
  s/list/lists/

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>