Remove unnecessary line wraps in e-mails sent by phpBB

E-mails sent by phpBB have line breaks in them at ca 75 characters, which causes those e-mails look messy on narrow screens. For example this is how a topic reply notification looks like on my mobile phone: screenshot

I think we should remove those line breaks and let e-mail clients wrap words based on screen width - this how modern email are formatted.

PS more info in this topic