Fix typo in docs/graceful-shutdown.md
Fix typo in docs/graceful-shutdown.md

Signed-off-by: Joowon Cheong <c288d17de9a7dfa0a739e35fa0c53fffb7d7c475@gmail.com>

davidvossel/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt