Add dashboard group for istio-csr, fix comment

[SgtCoDFish]

• Adds a couple of annotations which seem obvious (see https://github.com/kubernetes/test-infra/blob/master/testgrid/config.md)
• Fixes times given in comment on cron field; I mistakenly used BST rather than UTC
• Moves the new istio-csr dashboard to a group called "cert-manager-subprojects"

[inteon]

The PR looks good to me, I think the best way to figure out if it will work is to merge it. /approve /lgtm

[cert-manager-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: inteon

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[cert-manager-prow[bot]]

@SgtCoDFish: Updated the job-config configmap in namespace default at cluster default using the following files:

• key cert-manager-istio-csr-periodics.yaml using file config/jobs/cert-manager/istio-csr/cert-manager-istio-csr-periodics.yaml

In response to [this](https://github.com/cert-manager/testing/pull/1068): >- Adds a couple of annotations which seem obvious (see https://github.com/kubernetes/test-infra/blob/master/testgrid/config.md) >- Fixes times given in comment on cron field; I mistakenly used BST rather than UTC >- Moves the new istio-csr dashboard to a group called "cert-manager-subprojects" Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.

[SgtCoDFish]

It worked! https://testgrid.k8s.io/cert-manager-subprojects