Remove latest from test-cpanfile

The `latest` flavor is not available.

Author: atoomic

.github/workflows/test-cpanfile.yml

@@ -28,7 +28,6 @@ jobs:
           - '5.30'
           - '5.32'
           - '5.34'
-          - 'latest'
     name: Perl ${{ matrix.perl-version }}
     steps:
       - uses: actions/checkout@v2