media: docs: media: Fix imbalance of LaTeX group

The beginning part of the "existing HSV/HSL formats" table (line 7742)
reads:

  .. raw:: latex

      \begingroup
      \tiny
      \setlength{\tabcolsep}{2pt}

However, the ending part (line 7834) reads:

  .. raw:: latex

      \normalsize

Fix the imbalance by replacing the \normalsize with \endgroup.

Note:
    Actually, the imbalance is harmless and just results in an
    informative message near the bottom of userspace-api.log:

      (\end occurred inside a group at level 1)

      ### semi simple group (level 1) entered at line 70696 (\begingroup)
      ### bottom level

Link: https://lore.kernel.org/linux-media/b3eeec4d-1a34-0a1a-3097-1ddea3b5f1c8@gmail.com


Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>