Update r-conda.yml with actions/checkout@v3

[hechth]

Closes #205

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (25bf73b) 66.13% compared to head (2c8dbc0) 66.13%.

❗ Current head 2c8dbc0 differs from pull request most recent head 2aeef72. Consider uploading reports for the commit 2aeef72 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #206   +/-   ##
=======================================
  Coverage   66.13%   66.13%           
=======================================
  Files          23       23           
  Lines        2616     2616           
=======================================
  Hits         1730     1730           
  Misses        886      886           

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