Update ops to run planpreview cleaner at a fixed time

[nghialv]

What this PR does / why we need it:

• Fix the time to run the job to make it becomes more predictable.
• This also ensures that the job will be executed once per day even if the ops was restarted or deployed.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 32.08%. This pull request does not change code coverage.

[nakabonne]

/lgtm

[khanhtc1202]

🚀
/approve

[pipecd-bot]

This pull request is APPROVED by khanhtc1202.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.