Skip running vtadmin build for vitess tester workflow

[GuptaManan100]

Description

It was noticed that the vitess tester workflow while running make build was also building the vtadmin binaries. That however is not required since it doesn't actually run the vtadmin. Moreover, because of the lack of correct dependencies being installed the workflow fails sometimes https://github.com/vitessio/vitess/actions/runs/10043908851/job/27757759665. This PR fixes this issue.

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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