Make VISCtemplates require R >= 4.1.0 and drop R 4.0.4 from CI

[slager]

Description

Replicates FredHutch/VISCfunctions#134 for VISCtemplates and prepares for #310. Closes #333.

Related Issues

Provide links to any related GitHub issues.

Checklist

• This PR includes unit tests
• This PR establishes a new function or updates parameters in an existing function
  • The roxygen skeleton for this function has been updated using devtools::document
• I have updated NEWS.md to describe the proposed changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.14%. Comparing base (3a883b2) to head (2f4b355).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #334   +/-   ##
========================================
  Coverage    85.14%   85.14%           
========================================
  Files           10       10           
  Lines          377      377           
========================================
  Hits           321      321           
  Misses          56       56           

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[slager]

R version requirement was approved by team at yesterday's meeting, and the rest is CI-only updates. Merging!