contrib guide: update link
contrib guide: update link

The SIG-Release ephemera on issue workflow is moved to the devel guide.
Updating reference to it.

Signed-off-by: Tim Pepper <4807564e5a18784afafcf20dbdb5591e844b9075@vmware.com>

bgrant0607/community,kubernetes/community,kubernetes/community,pwittrock/community,bgrant0607/community,pwittrock/community,kubernetes/community