use new, improved r-universe URL schema

[cjyetman]

https://ropensci.org/blog/2023/01/30/runiverse-permanent-urls/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.90%. Comparing base (4cb56f6) to head (d440b69).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #104   +/-   ##
=======================================
  Coverage   61.90%   61.90%           
=======================================
  Files          21       21           
  Lines         756      756           
=======================================
  Hits          468      468           
  Misses        288      288           

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