Do not forward SDL_DROPFILE event

The event is handled by scrcpy.c, it is not necessary to send it to
screen or input_manager.

app/src/scrcpy.c

@@ -167,7 +167,7 @@ handle_event(SDL_Event *event, const struct scrcpy_options *options) {
                 action = ACTION_PUSH_FILE;
             }
             file_handler_request(&file_handler, action, file);
-            break;
+            goto end;
         }
     }