[release/3.1] Remove Kevin from CodeOwners (#44159)

.github/CODEOWNERS

 # Users referenced in this file will automatically be requested as reviewers for PRs that modify the given paths.
 # See https://help.github.com/articles/about-code-owners/
 
-*                               @Pilchie
 /global.json                    @dotnet/aspnet-build
 /.azure/                        @dotnet/aspnet-build
 /.config/                       @dotnet/aspnet-build