examples: increase stack size in http_request

Previously the stack size was 2048 bytes, which caused stack overflow
to be detected after one or two runs of the example.

examples/protocols/http_request/main/http_request_example_main.c

@@ -176,5 +176,5 @@ void app_main()
 {
     ESP_ERROR_CHECK( nvs_flash_init() );
     initialise_wifi();
-    xTaskCreate(&http_get_task, "http_get_task", 2048, NULL, 5, NULL);
+    xTaskCreate(&http_get_task, "http_get_task", 4096, NULL, 5, NULL);
 }