Revert "lang: support direct video inference" (#12038)

docs/references/frontend/frontend_tutorial.ipynb

@@ -33,7 +33,7 @@
     "from sglang import assistant, function, gen, system, user\n",
     "from sglang import image\n",
     "from sglang import RuntimeEndpoint\n",
-    "from sglang.lang.api import set_default_backend, video\n",
+    "from sglang.lang.api import set_default_backend\n",
     "from sglang.srt.utils import load_image\n",
     "from sglang.test.doc_patch import launch_server_cmd\n",
     "from sglang.utils import print_highlight, terminate_process, wait_for_server\n",
@@ -421,11 +421,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "jupyter": {
-     "is_executing": true
-    }
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "@function\n",
@@ -440,30 +436,6 @@
     "print_highlight(state[\"answer\"])"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "Ask a question about a video"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "@function\n",
-    "def video_qa(s, video_file, question):\n",
-    "    s += user(video(video_file) + question)\n",
-    "    s += assistant(gen(\"answer\", max_tokens=256))\n",
-    "\n",
-    "\n",
-    "video_url = \"https://raw.githubusercontent.com/sgl-project/sgl-test-files/refs/heads/main/videos/jobs_presenting_ipod.mp4\"\n",
-    "state = video_qa(video_url, \"What is in the video?\")\n",
-    "print_highlight(state[\"answer\"])"
-   ]
-  },
   {
    "cell_type": "code",
    "execution_count": null,