Documentation: networking/tcp_ao: typo and grammar fixes

Fix multiple grammatical issues and add a missing period to improve
readability.

Signed-off-by: Leo Stone <leocstone@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240929005001.370991-1-leocstone@gmail.com


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