handleFileRead: Skip duplicate FS check

Since we validate the file existence ourselves, no need to have
AsyncWebServer do it again.

wled00/file.cpp

@@ -433,7 +433,7 @@ bool handleFileRead(AsyncWebServerRequest* request, String path){
   }
   #endif
   if(WLED_FS.exists(path) || WLED_FS.exists(path + ".gz")) {
-    request->send(WLED_FS, path, String(), request->hasArg(F("download")));
+    request->send(request->beginResponse(WLED_FS, path, {}, request->hasArg(F("download")), {}));
     return true;
   }
   return false;