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_lt.yml

@@ -1,7 +1,6 @@
-unknown_user: '&cNaudotojo nera duombazeje'
+unknown_user: '&cVartotojas neprisiregistraves'
 unsafe_spawn: '&6Atsijungimo vieta nesaugi, perkeliame jus i atsiradimo vieta.'
 not_logged_in: '&cTu neprisijunges!'
-reg_voluntarily: '&ePrisiregistruokite: /register slaptazodis pakartotiSlaptazodi'
 usage_log: '&eKomandos panaudojimas: /login slaptazodis'
 wrong_pwd: '&cNeteisingas slaptazosdis'
 unregistered: '&aSekmingai issiregistravote!'
@@ -19,7 +18,6 @@ login_msg: '&ePrasome prisijungti: /login slaptazodis'
 reg_msg: '&ePrasome prisiregistruoti: /register slaptazodis pakartotiSlaptazodi'
 usage_unreg: '&ePanaikinti registracija: "/unregister slaptazodis"'
 pwd_changed: '&aSlaptazodis pakeistas'
-user_unknown: '&cVartotojas neprisiregistraves'
 password_error: '&cSlaptazodziai nesutampa'
 invalid_session: '&cSesijos laikai nesutampa, prasome palaukti kol secija baigsis.'
 reg_only: '&cTik prisiregistravusiem zaidejams: apsilankykite: http://example.com tam kad uzsiregistruoti.'
@@ -74,4 +72,4 @@ kick_fullserver: '&cServeris yra pilnas, Atsiprasome.'
 # 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'