UPDATECLI: Update cert-manager

[didactikbot]

Update cert-manager npins.

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cert-manager Update

cert-manager npins update v1.20.1

ran shell command "set -e\nnix run nixpkgs#npins -- add --name cert-manager github cert-manager cert-manager --at v1.20.1\nnix-shell shell.nix --run \"buildCertManager 'v1.20.1'\"\n"

v1.20.1

v1.20.1 fixes an issue for OpenShift users that has to do with the finalizer RBAC, bumps gRPC to address a reported non-affecting vulnerability, and fixes a duplicate `parentRef` bug when both issuer config and annotations are present (Gateway API).

### Bug or Regression

- Fixed duplicate `parentRef` bug when both issuer config and annotations are present. (#8658, @hjoshi123)
- Add missing issuer finalizer RBAC to the order controller to support owner references. This was preventing OpenShift users from being able to upgrade to v1.20.0. (#8655, @erikgb)
- Bump google.golang.org/grpc to fix vulnerability reported by scanners. This isn't a vulnerability that affects cert-manager, but we are bumping it because it is reported by scanners. (#8657, @erikgb)

GitHub Action workflow link

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