quiet the aaf adapter test to clean up test output

[ssteinbach]

The AAF adapter had a unit test that was printing to stdout. This test quiets that output and checks the result against an expected string.

[codecov-io]

Codecov Report

Merging #893 (4148e84) into master (6ed3b56) will decrease coverage by 0.47%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #893      +/-   ##
==========================================
- Coverage   86.65%   86.18%   -0.48%     
==========================================
  Files         183      183              
  Lines       17879    17705     -174     
  Branches     1972     1972              
==========================================
- Hits        15493    15259     -234     
- Misses       1902     1948      +46     
- Partials      484      498      +14     

Flag	Coverage Δ
unittests	86.18% <100.00%> (-0.40%)	⬇️

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Impacted Files	Coverage Δ
...elineio_contrib/adapters/tests/test_aaf_adapter.py	98.21% <100.00%> (+0.04%)	⬆️
tests/test_plugin_detection.py	84.31% <0.00%> (-9.81%)	⬇️
...lineio_contrib/adapters/tests/test_fcpx_adapter.py	89.74% <0.00%> (-6.46%)	⬇️
...-opentimelineio/opentimelineio/core/_core_utils.py	79.07% <0.00%> (-5.22%)	⬇️
...-opentimelineio/opentimelineio/console/otiostat.py	67.81% <0.00%> (-3.62%)	⬇️
...-opentimelineio/opentimelineio/adapters/adapter.py	87.12% <0.00%> (-1.99%)	⬇️
contrib/opentimelineio_contrib/adapters/xges.py	79.21% <0.00%> (-1.84%)	⬇️
...ntimelineio/opentimelineio-bindings/otio_tests.cpp	71.92% <0.00%> (-1.76%)	⬇️
...ineio_contrib/adapters/tests/tests_xges_adapter.py	90.65% <0.00%> (-1.19%)	⬇️
...ontrib/opentimelineio_contrib/adapters/kdenlive.py	82.23% <0.00%> (-1.16%)	⬇️
... and 26 more

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