af_unix: Remove unnecessary brackets around CONFIG_AF_UNIX_OOB.

[ Upstream commit 4edf21aa

 ]

Let's remove unnecessary brackets around CONFIG_AF_UNIX_OOB.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Link: https://lore.kernel.org/r/20220317032308.65372-1-kuniyu@amazon.co.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 2aab4b96

 ("af_unix: fix struct pid leaks in OOB support")
Signed-off-by: Sasha Levin <sashal@kernel.org>