Documentation: networking: correct possessive "its"

Change occurrences of "it's" that are possessive to "its"
so that they don't read as "it is".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20220829235414.17110-1-rdunlap@infradead.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>