Fix code after changes in scoringutils

[nikosbosse]

In epiforecasts/scoringutils#903 we changed the scoringutils behaviour surrounding the default metrics. This PR fixes the current code to conform with the new update.

I'll make additional suggestions in separate PRs.

I also fixed a failing test where scoringutils produced a warning in expect_equal. Sorry for that! Converting the data to data.frames avoids issues with scoringutils internally validating things it shouldn't be validating.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 93.43%. Comparing base (24b02b3) to head (937187a).
Report is 104 commits behind head on main.

Files with missing lines	Patch %	Lines
R/score_model_out.R	78.57%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            main      #52       +/-   ##
==========================================
+ Coverage   0.00%   93.43%   +93.43%     
==========================================
  Files          2        5        +3     
  Lines         31      198      +167     
==========================================
+ Hits           0      185      +185     
+ Misses        31       13       -18     

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[elray1]

lgtm!