.github: Fix cilium project management for v1.9
.github: Fix cilium project management for v1.9

Commit a02744cbe274 ("README: update security releases") bumped the
README for v1.9.0, but missed the github actions, which meant that
labeling PRs for backport to v1.9.1 would not trigger the maintainer's
little helper to put the PRs in the appropriate project.

Bump the project to the v1.9.1 project to fix this.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

michi-covalent/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium