docs: fix Co-Developed-by docs

docs: fix Co-Developed-by docs

The accepted terminology will be Co-developed-by therefore lose the
capital letter from now on.

Link: http://lkml.kernel.org/r/1544808928-20002-2-git-send-email-jorge.ramirez-ortiz@linaro.org
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Acked-by: Himanshu Jha <himanshujha199640@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Niklas Cassel <niklas.cassel@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>