add 'exempt-pr-labels' for 'not-auto-close' PRs

[t-kikuc]

What this PR does / why we need it:

• This PR stops staling PRs with the 'not-auto-close' tag.

• Background:

  • Use repository settings from piped config #4739 was closed unintentionally by the stale action although the not-auto-close tag was assigned.
  • Cause: We needed exempt-pr-labels, not only exempt-issue-labels.
    • cf. https://github.com/actions/stale?tab=readme-ov-file#list-of-input-options

[khanhtc1202]

👍

[ffjlabo]

🚀

[t-kikuc]

Reopen for the flaky test...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 22.78%. Comparing base (f44dbf7) to head (be9a912).
Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #5134       +/-   ##
===========================================
+ Coverage        0   22.78%   +22.78%     
===========================================
  Files           0      412      +412     
  Lines           0    43827    +43827     
===========================================
+ Hits            0     9987     +9987     
- Misses          0    33053    +33053     
- Partials        0      787      +787     

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