Use modern asyncio bootstrap in examples

[frenck]

Proposed Changes

This library already requires Python 3.8, so no reason to keep the old bootstrap around (that spawns a deprecation warning in Python 3.10 anyways).

[codecov]

Codecov Report

Merging #466 (93528cd) into main (cb07293) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #466   +/-   ##
=======================================
  Coverage   57.80%   57.80%           
=======================================
  Files           4        4           
  Lines         538      538           
  Branches      116      116           
=======================================
  Hits          311      311           
  Misses        207      207           
  Partials       20       20           

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