fix stale workflow

[RunningLeon]

Motivation

Stale workflow should have write permission to do job such close issues per here.

Modification

Reset to default permission, which changed in PR #1548

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Base: 44.74% // Head: 44.74% // No change to project coverage 👍

Coverage data is based on head (0e2d10c) compared to base (12b3d18).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1713   +/-   ##
=======================================
  Coverage   44.74%   44.74%           
=======================================
  Files         356      356           
  Lines       12739    12739           
  Branches     1800     1800           
=======================================
  Hits         5700     5700           
  Misses       6646     6646           
  Partials      393      393           

Flag	Coverage Δ
unittests	44.74% <ø> (ø)

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