[Minor] Use utf8 length for subject
[Minor] Use utf8 length for subject

andrejzverev/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,minaevmike/rspamd,minaevmike/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,AlexeySa/rspamd,AlexeySa/rspamd