fix #864: change macos runner to macos-latest

[morrison12]

Change macOS runner to macos-latest. Another possibility is macos-11 and manually changing to macos-12 later.

[codecov[bot]]

Codecov Report

Merging #865 (83525b0) into 2.x (5fedec4) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##              2.x     #865   +/-   ##
=======================================
  Coverage   91.68%   91.68%           
=======================================
  Files         122      122           
  Lines        7580     7580           
=======================================
  Hits         6950     6950           
  Misses        630      630           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.