toradio, fromradio OPTIONS handler: fix sending proper HTTP response.

Before this (missing response):
$ curl -v -X OPTIONS http://meshtastic.local/api/v1/fromradio
* Host meshtastic.local:80 was resolved.
* IPv6: (none)
* IPv4: 192.168.0.19
*   Trying 192.168.0.19:80...
* Connected to meshtastic.local (192.168.0.19) port 80
* using HTTP/1.x
> OPTIONS /api/v1/fromradio HTTP/1.1
> Host: meshtastic.local
> User-Agent: curl/8.14.1
> Accept: */*
>
* Request completely sent off
* Empty reply from server
* shutting down connection #0
curl: (52) Empty reply from server

After this (proper HTTP 204 response):
$ curl -v -X OPTIONS http://meshtastic.local/api/v1/fromradio
* Host meshtastic.local:80 was resolved.
* IPv6: (none)
* IPv4: 192.168.0.19
*   Trying 192.168.0.19:80...
* Connected to meshtastic.local (192.168.0.19) port 80
* using HTTP/1.x
> OPTIONS /api/v1/fromradio HTTP/1.1
> Host: meshtastic.local
> User-Agent: curl/8.14.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 204 OK
< Content-Type: application/x-protobuf
< Access-Control-Allow-Origin: *
< Access-Control-Allow-Methods: GET
< X-Protobuf-Schema: https://raw.githubusercontent.com/meshtastic/protobufs/master/meshtastic/mesh.proto
<
* Connection #0 to host meshtastic.local left intact

This is related to #5385.

Author: cpatulea

src/mesh/http/ContentHandler.cpp

@@ -173,7 +173,7 @@ void handleAPIv1FromRadio(HTTPRequest *req, HTTPResponse *res)
 
     if (req->getMethod() == "OPTIONS") {
         res->setStatusCode(204); // Success with no content
-        // res->print(""); @todo remove
+        res->print("");
         return;
     }
 
@@ -223,7 +223,7 @@ void handleAPIv1ToRadio(HTTPRequest *req, HTTPResponse *res)
 
     if (req->getMethod() == "OPTIONS") {
         res->setStatusCode(204); // Success with no content
-        // res->print(""); @todo remove
+        res->print("");
         return;
     }