Update docs for drop-invalid-packets and response-origin-only-with-rfc5780 (#1918)

I attempted to use `make-man.sh` and it added a ton of man macro
formatting back in,
since it was a minor targeted fix I just updated `turnserver.1`
manually.

Fixes: https://github.com/coturn/coturn/issues/1917

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Co-authored-by: Corey Siltala <csiltala@atcorp.com>
Co-authored-by: Pavel Punsky <eakraly@users.noreply.github.com>