Fix production WSFE TLS compatibility

[eeng]

Summary

• preserve the OpenSSL security-level cipher expression required by ARCA production WSFE
• scope the compatibility setting to the production WSFE client
• document the temporary security tradeoff and cover it with regression tests

Verification

• mise run test — 73 examples, 0 failures
• production smoke test outside the sandbox:
  bundle exec ruby -Ilib -e 'require "afipws"; ws = Afipws::WSFE.new(env: :production); p ws.dummy'\n- result: {app_server: "OK", db_server: "OK", auth_server: "OK"}