[Style] Fix golangci-lint rule: unconvert

[MortalHappiness]

Why are these changes needed?

Based on https://github.com/ray-project/kuberay/pull/2128, there are some rules that need manual fixing. This PR fixes the rule: unconvert

See https://golangci-lint.run/usage/linters/ for details.

Related issue number

N/A

Checks

• [x] I've made sure the tests are passing.
• Testing Strategy
  • [ ] Unit tests
  • [x] Manual tests
  • [ ] This PR is not tested :(

[kevin85421]

Weird. The RayJob e2e tests have already finished, as shown in the screenshot, but it still shows that they are "in progress". I think it may be GitHub Actions's issue.