virtctl.sh: remove script and generate error

[dhiller]

What this PR does / why we need it:

As discussed in #1277 the script virtctl.sh exists only as an artifact before kubevirtci was moved to it's own repository. It has been replaced by a kubevirt/kubevirt script that does the same, which should be used further on.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1277

Special notes for your reviewer:
/cc @brianmcarey

[kubevirt-bot]

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[kubevirt-bot]

@dhiller: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
check-provision-k8s-1.31-s390x	fa699d5	link	false	/test check-provision-k8s-1.31-s390x

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