fix: Spawning tokio task outside reactor

[orlp]

Silly mistake by me.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@18c8da0). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/execute.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #23884   +/-   ##
=======================================
  Coverage        ?   81.40%           
=======================================
  Files           ?     1665           
  Lines           ?   224713           
  Branches        ?     2882           
=======================================
  Hits            ?   182937           
  Misses          ?    41058           
  Partials        ?      718           

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