[Fix][Release] Fix Krew release indenetation error

[MortalHappiness]

Why are these changes needed?

As title.

The sha256 should be indented, otherwise there will be yaml format error.

Related issue number

Checks

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

[kevin85421]

Why can’t we find the issue in the previous PRs? Is there anything we can improve to avoid this kind of issue?

[MortalHappiness]

Why can’t we find the issue in the previous PRs? Is there anything we can improve to avoid this kind of issue?

Because this error can only be caught by actually running the GitHub Actions, it's difficult to backport a fix to a previous tag once the error occurs. In the last release (v1.3.2), the action run failed, so we manually created a PR to the krew-index repo and then added a fix to the master branch of the KubeRay repo. However, it seems that PR still had issues. We couldn't open a PR to the release-1.3 branch because the v1.3.2 tag had already been created, and it doesn't include the newly merged PR. At the same time, we didn't want to create another tag, so we had to create the PR manually. That's why this kind of bug is hard to catch.