remove all gke-staging-1-8-1-9 test grid tabs

[crimsonfaith91]

This PR removes all gke-staging-1-8-1-9 test grid tabs because 1.8 is not available anymore.

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[krzyzacy]

also remove entries from https://github.com/kubernetes/test-infra/blob/master/config/jobs/gke/gke-staging-upgrade.yaml

[crimsonfaith91]

@krzyzacy Removed all the items accordingly.

[krzyzacy]

/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: crimsonfaith91, krzyzacy

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[k8s-ci-robot]

@crimsonfaith91: Updated the job-config configmap using the following files:

• key gke-staging-upgrade.yaml using file config/jobs/gke/gke-staging-upgrade.yaml
• key gke-staging.yaml using file config/jobs/gke/gke-staging.yaml

In response to this:

This PR removes all gke-staging-1-8-1-9 test grid tabs because 1.8 is not available anymore.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.