fix(loggin): Incorrect FPS computation fixed

Corrected and tested change in FPS computation, suggested by @me-no-dev and found working with correct numbers.

Previously, last_frame was only updated once at the beginning of stream_handler,
leading to incorrect FPS and avg_frame_time computation.

This commit ensures last_frame is updated on each iteration after last FPS computation,
resulting in accurate FPS logging.

Fixes #10920

Author: TNeutron

libraries/ESP32/examples/Camera/CameraWebServer/app_httpd.cpp

@@ -281,6 +281,8 @@ static esp_err_t stream_handler(httpd_req_t *req) {
     int64_t fr_end = esp_timer_get_time();
 
     int64_t frame_time = fr_end - last_frame;
+    last_frame = fr_end;
+
     frame_time /= 1000;
 #if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
     uint32_t avg_frame_time = ra_filter_run(&ra_filter, frame_time);