doc: module: Fix documented type of namespace

Since commit cdd30ebb ("module: Convert symbol namespace to string
literal") the namespace has to be a string. Fix accordingly.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/6fe15069c01b31aaa68c6224bec2df9f4a449858.1733305665.git.ukleinek@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241230142357.3203913-5-u.kleine-koenig@baylibre.com