Fix Release env of site in publish_site workflow

[t-kikuc]

What this PR does / why we need it:

Without this PR, the published site still shows Generated, although https://github.com/pipe-cd/pipecd/pull/5192 is merged.

Which issue(s) this PR fixes:

Follows #5192

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 22.86%. Comparing base (ac32fda) to head (7a5b3da). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5195 +/- ## ======================================= Coverage 22.85% 22.86% ======================================= Files 420 420 Lines 45245 45245 ======================================= + Hits 10340 10344 +4 + Misses 34109 34106 -3 + Partials 796 795 -1 ```

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