Remove macOS 10.13 from the build matrix
Remove macOS 10.13 from the build matrix

We support N-2 macOS releases so 10.13 can be dropped now that Big Sur
is out.

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

MsysTechnologiesllc/chef,nvwls/chef,tas50/chef-1,chef/chef,tas50/chef-1,gene1wood/chef,gene1wood/chef,mattray/chef,nvwls/chef,mwrock/chef,nvwls/chef,gene1wood/chef,mattray/chef,gene1wood/chef,MsysTechnologiesllc/chef,mattray/chef,chef/chef,mattray/chef,tas50/chef-1,mwrock/chef,mattray/chef,chef/chef,tas50/chef-1,chef/chef,mwrock/chef,nvwls/chef,mwrock/chef,MsysTechnologiesllc/chef,nvwls/chef,nvwls/chef,MsysTechnologiesllc/chef