Don't repeatedly append onions map

src/freedombone-app-xmpp

 function xmpp_onion_addresses {
     filename="$1"
 
+    sed -i '/onions_map = {/,/};/d' "$filename"
+
     { echo 'onions_map = {';
       echo '  ["anonymitaet-im-inter.net"] = "rwf5skuv5vqzcdit.onion";';
       echo '  ["autistici.org"] = "wi7qkxyrdpu5cmvr.onion";';