Remove push-build.sh

[saschagrunert]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Removing the script since it's not used any more.

Which issue(s) this PR fixes:

None

Special notes for your reviewer:

/hold

for consensus

Does this PR introduce a user-facing change?

Removed the long time deprecated `push-build.sh`.

[k8s-ci-robot]

@saschagrunert: Adding label: do-not-merge/blocked-paths because PR changes a protected file.

Reasons for blocking this PR:

[Changes to push-build.sh will immediately affect the Kubernetes CI. This PR must be explicitly approved by SIG Release repo admins.]

• push-build.sh

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: saschagrunert

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• OWNERS [saschagrunert]

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[k8s-ci-robot]

@saschagrunert: 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
pull-release-cluster-up	ad8b566	link	true	/test pull-release-cluster-up

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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