parse-maintainers: Mark as executable

[ Upstream commit 611d61f9ac99dc9e1494473fb90117a960a89dfa ]

This makes the script more convenient to run.
Signed-off-by: NJonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>