[HZ-5259] Fixed sql_async_example.py

[yuce]

sql_async_example.py exits too early, before having a change to print the result rows.
Added a small sleep to make sure the rows are printed before exit.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.59%. Comparing base (432508c) to head (2ed5a75).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #765      +/-   ##
==========================================
- Coverage   94.61%   94.59%   -0.02%     
==========================================
  Files         393      393              
  Lines       25056    25056              
==========================================
- Hits        23707    23702       -5     
- Misses       1349     1354       +5     

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[yuce]

Trivial, merging it myself.