Signal's send() used 'text' instead of 'content' and 'reply_to_message_id'
instead of 'reply_to', mismatching BasePlatformAdapter.send(). Callers in
gateway/run.py use keyword args matching the base interface, so Signal's
send() was missing its required 'text' positional arg.
Fixes: 'SignalAdapter.send() missing 1 required positional argument: text'
d6ab35c1a3