Restore default handle's encoding to be utf8
Restore default handle's encoding to be utf8

- This was the test originally added 13 days ago
- The check was changed to look for Nil, but that
    also means the handle is in binary mode, yet default
    mode was utf8
- Now we changed[^1] the default to be properly visible and
    .encoding method returns 'utf8' again

[1] https://github.com/rakudo/rakudo/commit/95b4e5d5c3

bitrauser/roast,dogbert17/roast,bitrauser/roast,perl6/roast,dogbert17/roast