Remove all <...> text blocks in replies

[ofa-]

I noticed that in TB 102.11.0 (at least, on Ubuntu) I get mangled links and email addresses in plain-text replies to HTML mails. It looks as though TB is adding blocks of the form <link> or <email> to links or emails in the original HTML email when converting it to plain text; and this gets nested with replies piling up.

This single-commit PR removes the extraneous bloat in plain-text replies.