Shortened ?loo_subsample title and slightly edited description

[vinniott]

Fixes #338

Note that:

• I only tested devtools::check(vignettes = F)
• I slightly edited the description, too.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.78%. Comparing base (d5e23dd) to head (1e13153).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #339   +/-   ##
=======================================
  Coverage   92.78%   92.78%           
=======================================
  Files          31       31           
  Lines        2992     2992           
=======================================
  Hits         2776     2776           
  Misses        216      216           

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[jgabry]

Thank you! I agree about simplifying the title. I made one comment with a suggested change.

[jgabry]

You don't need @title if the text is in the first line of the roxygen comment block (it will automatically use @title for you).

Also, I think we should keep "using subsampling" in the title since that's what distinguishes loo_subsample, but I agree we should get rid of the rest of the long title and put that info in the description.

[vinniott]

thanks!

[jgabry]

Thank you! Merging the PR now