Tidy up asyncio examples.

[Dreamsorcerer]

Fixes #2419.

I haven't received any feedback to suggest there is a reason for these oddities, so here are the suggested changes to the asyncio examples.

[codecov-commenter]

Codecov Report

Base: 92.03% // Head: 91.99% // Decreases project coverage by -0.04% ⚠️

Coverage data is based on head (34d3659) compared to base (bea00b1).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2431      +/-   ##
==========================================
- Coverage   92.03%   91.99%   -0.05%     
==========================================
  Files         110      110              
  Lines       28737    28737              
==========================================
- Hits        26448    26436      -12     
- Misses       2289     2301      +12     

Impacted Files	Coverage Δ
tests/test_cluster.py	96.62% <0.00%> (-0.35%)	⬇️
tests/test_asyncio/test_cluster.py	96.95% <0.00%> (-0.34%)	⬇️
redis/asyncio/connection.py	87.01% <0.00%> (-0.12%)	⬇️

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