release.sh: use "Cc:" rather than "CC:"
release.sh: use "Cc:" rather than "CC:"

git-send-email ignores CC headers, so using that to send announcements generated
by release.sh fails to actually carbon copy the Cc'd list.  Use Cc instead.

Signed-off-by: Aaron Plattner <7c39395e2e801146cdbd7fb4a41282e4f38db44e@nvidia.com>
Reviewed-by: Gaetan Nadon <8a8cc541338200f67d4d0bcb65c78b6166649462@videotron.ca>

freedesktop-unofficial-mirror/xorg__util__modular,freedesktop-unofficial-mirror/xorg__util__modular,freedesktop-unofficial-mirror/xorg__util__modular