💚 Fix CI coverage reporting

[techouse]

It seems that the coverage reports haven't been working for a while.

Hopefully this will fix it.

[codecov]

Codecov Report

Merging #423 (d38ae76) into develop (b8fd63a) will increase coverage by 4.44%.
The diff coverage is 95.09%.

@@             Coverage Diff             @@
##           develop     #423      +/-   ##
===========================================
+ Coverage    89.18%   93.63%   +4.44%     
===========================================
  Files            5        8       +3     
  Lines          333      440     +107     
===========================================
+ Hits           297      412     +115     
+ Misses          36       28       -8     

Impacted Files	Coverage Δ
chopper/lib/src/interceptor.dart	73.33% <71.42%> (-7.16%)	⬇️
chopper/lib/src/response.dart	88.88% <88.88%> (+22.22%)	⬆️
chopper/lib/src/base.dart	94.73% <94.73%> (+1.08%)	⬆️
chopper/lib/src/http_logging_interceptor.dart	95.91% <95.91%> (ø)
chopper/lib/src/extensions.dart	100.00% <100.00%> (ø)
chopper/lib/src/request.dart	100.00% <100.00%> (+8.53%)	⬆️
chopper/lib/src/utils.dart	100.00% <100.00%> (ø)
chopper_built_value/lib/chopper_built_value.dart	96.66% <100.00%> (ø)

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