[media] dev-overlay.rst: don't ident a note

There's one note there that it is indented for no good reason.
Fix it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/v4l/dev-overlay.rst

@@ -238,7 +238,7 @@ exceeded are undefined. [#f3]_
     :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`,
     :ref:`framebuffer-flags`).
 
-    .. note::
+.. note::
 
    This field was added in Linux 2.6.23, extending the
    structure. However the :ref:`VIDIOC_[G|S|TRY]_FMT <VIDIOC_G_FMT>`