[Ubuntu] remove toolchain test repo

[mikhailkoliada]

Description

As described in the announcement

Related issue: https://github.com/actions/runner-images/issues/9679

Check list

• [ ] Related issue / work item is attached
• [ ] Tests are written (if applicable)
• [ ] Documentation is updated (if applicable)
• [ ] Changes are tested and related VM images are successfully generated

[mikhailkoliada]

/azp run ubuntu2004, ubuntu2204, ubuntu2404

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