docs: parse-headers.rst: remove uneeded parenthesis

docs: parse-headers.rst: remove uneeded parenthesis

As pointed by Randy, the parenthesis there is not needed and it
violates the document coding style.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Closes: https://lore.kernel.org/linux-doc/9d709020-03fe-467c-be7f-d5ee251bb79a@infradead.org/
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <e5de9f7b1f6a963b2912574a65495c47cfbb13ba.1762878176.git.mchehab+huawei@kernel.org>