Issue 428 fix metrics table

[nikosbosse]

Fixes #428

As discussed in #428, there were a few duplicate table entries in the metrics table. I initially thought these were caused by the way that the data was constructed, but it turns out the solution was just to call unique() on the table before using it in the vignette (because other columns like the name of the function, which make the table non-unique, were removed and are not shown in the vignette)

There were additional issues with the table raised by JSS reviewers. These concerned e.g. the orientation of the log score (and making it clear that we're using the negative log likelihood). In addition, I corrected a few spelling and grammatical errors and changed "true value" to "observed value".

We will eventually have to rework this table a bit (see #415 (which is mostly a stub issue at this point)), but I think it makes sense to fix errors now and spend time later to think about how to update the table.

[seabbs]

Looks good. Why not do this in a single pipe? This PR has no associated news update.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e849d60) 90.87% compared to head (ce29ee5) 90.91%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #489      +/-   ##
==========================================
+ Coverage   90.87%   90.91%   +0.03%     
==========================================
  Files          22       23       +1     
  Lines        1392     1398       +6     
==========================================
+ Hits         1265     1271       +6     
  Misses        127      127              

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[nikosbosse]

Added a news item. There are two pipes now because the previous single pipe had a call to nrow(data), but the numbers of rows for the data was changed throughout the pipe by the call to unique(). I guess %>% would have allowed a call to nrow(.)? But not sure there is a good way to replicate that with |>