Remove redundant and unused message

- Remove 'reg_voluntarily'
- Remove 'user_unknown' in favor of 'unknown_user' - but move text from old 'user_unknown' to 'unknown_user'

Found by @Twonox

src/main/resources/messages/messages_id.yml

@@ -1,7 +1,6 @@
-unknown_user: '&cTidak dapat menemukan user yg diminta di database!'
+unknown_user: '&cUser ini belum terdaftar!'
 unsafe_spawn: '&cLokasi quit kamu tidak aman, kamu telah diteleport ke titik spawn world.'
 not_logged_in: '&cKamu belum login!'
-reg_voluntarily: 'Kamu bisa register menggunakan command "/register <password> <ulangiPassword>"'
 usage_log: '&cUsage: /login <password>'
 wrong_pwd: '&cPassword salah!'
 unregistered: '&cUnregister berhasil!'
@@ -17,7 +16,6 @@ error: '&4Terjadi kesalahan tak dikenal, silahkan hubungi Administrator!'
 login_msg: '&cSilahkan login menggunakan command "/login <password>"'
 reg_msg: '&3Silahkan mendaftar ke server menggunakan command "/register <password> <ulangiPassword>"'
 pwd_changed: '&2Berhasil mengubah password!'
-user_unknown: '&cUser ini belum terdaftar!'
 password_error: '&cPassword tidak cocok, silahkan periksa dan ulangi kembali!'
 password_error_nick: '&cKamu tidak bisa menggunakan namamu sebagai password, silahkan coba yg lain...'
 password_error_unsafe: '&cPassword yg kamu pilih tidak aman, silahkan coba yg lain...'
@@ -74,4 +72,4 @@ antibot_auto_disabled: '&2[AntiBotService] AntiBot dimatikan setelah %m menit!'
 # TODO incomplete_email_settings: 'Error: not all required settings are set for sending emails. Please contact an admin.'
 # TODO email_send_failure: 'The email could not be sent. Please contact an administrator.'
 # TODO recovery_code_sent: 'A recovery code to reset your password has been sent to your email.'
-# TODO recovery_code_incorrect: 'The recovery code is not correct! Use /email recovery [email] to generate a new one'
+# TODO recovery_code_incorrect: 'The recovery code is not correct! Use /email recovery [email] to generate a new one'