tests: remove timeout from async tests

[P403n1x87]

With the latest changes to Austin there should be no need for the timeout argument, so we remove it.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (36871cc) 73.83% compared to head (31697b0) 73.84%.
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #26   +/-   ##
=======================================
  Coverage   73.83%   73.84%           
=======================================
  Files          16       16           
  Lines        1464     1472    +8     
  Branches      215      215           
=======================================
+ Hits         1081     1087    +6     
- Misses        321      323    +2     
  Partials       62       62           

Files	Coverage Δ
austin/aio.py	89.65% <100.00%> (ø)
austin/cli.py	79.26% <100.00%> (+0.25%)	⬆️
austin/format/mojo.py	87.23% <100.00%> (+0.27%)	⬆️
austin/simple.py	88.00% <100.00%> (-3.84%)	⬇️
austin/threads.py	88.88% <100.00%> (ø)
austin/__init__.py	71.01% <50.00%> (ø)

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