Switch colab pip install to git

colab/demo.ipynb

@@ -120,7 +120,8 @@
         "\n",
         "# Install nerfstudio\n",
         "%cd /content/\n",
-        "!pip install nerfstudio"
+        "# !pip install nerfstudio\n",
+        "!pip install git+https://github.com/nerfstudio-project/nerfstudio.git"
       ]
     },
     {