Fix close stale value to be relative

[dmathieu]

It appears the close value is relative to the issue being marked as stale.
Which makes sense. Marking as stale updates the issue, so we'd have to wait for 2 more years before closing.

This is the core equivalent of open-telemetry/opentelemetry-go-contrib#6943

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.8%. Comparing base (0997b5f) to head (f1366c3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6451     +/-   ##
=======================================
- Coverage   81.8%   81.8%   -0.1%     
=======================================
  Files        283     283             
  Lines      24910   24910             
=======================================
- Hits       20383   20382      -1     
- Misses      4122    4123      +1     
  Partials     405     405             

see 2 files with indirect coverage changes

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[dmathieu]

Merging as a trivial PR