test: replace fixturesDir with common.fixtures

In test-tls-honorcipherorder.js, use common.fixtures instead of
common.fixturesDir.

PR-URL: https://github.com/nodejs/node/pull/15907


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>