Fix failing GitHub Actions

[Bisaloo]

Some of the GHA failures in #46 are not due to my changes but to an issue with the workflows currently on main. In short, apt-get update needs to run before apt-get install. Reordering the steps fixes this because setup-r already runs apt-get update.

[codecov]

Codecov Report

Merging #47 (e5f91ae) into main (6a5f69e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #47   +/-   ##
=======================================
  Coverage   97.23%   97.23%           
=======================================
  Files          17       17           
  Lines        1701     1701           
=======================================
  Hits         1654     1654           
  Misses         47       47           

[sbfnk]

thanks!