Update minimum aiohttp version. Fixes GH-35.

[kmike]

Fix #35. The wierd thing is that brotli support is mentioned in aiohttp 3.7.3 changelog. But anyways, bumping the version won't hurt.

[codecov-commenter]

Codecov Report

Merging #36 (6975f2c) into main (1ac47c6) will not change coverage.
The diff coverage is n/a.

❗ Current head 6975f2c differs from pull request most recent head 6b7a148. Consider uploading reports for the commit 6b7a148 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #36   +/-   ##
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  Coverage   37.15%   37.15%           
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  Files           9        9           
  Lines         323      323           
  Branches       38       38           
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  Hits          120      120           
  Misses        203      203