fix: dispose window scheduler

[bednar]

Closes #640

Proposed Changes

Dispose scheduler when disposing write_api.

Checklist

• [x] CHANGELOG.md updated
• [x] Rebased/mergeable
• [x] pytest tests completes successfully
• [x] Commit messages are conventional
• [x] Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

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

Comparison is base (293ed7f) 90.40% compared to head (46ec063) 90.42%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #641      +/-   ##
==========================================
+ Coverage   90.40%   90.42%   +0.01%     
==========================================
  Files          39       39              
  Lines        3503     3509       +6     
==========================================
+ Hits         3167     3173       +6     
  Misses        336      336              

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