Remove duplicate imports in DensePose tutorial

Summary: We were importing torch, torchvision, PyTorch3D, and sys twice. This is just removing the duplicate (unneeded) imports

Reviewed By: theschnitz

Differential Revision: D24479270

fbshipit-source-id: 1048732f65242eb776c3eef537cb1ae58815c1eb

docs/tutorials/render_densepose.ipynb

@@ -55,14 +55,6 @@
     "    !pip install pytorch3d\n",
     "else:\n",
     "    !pip install 'git+https://github.com/facebookresearch/pytorch3d.git@stable'\n",
-    "!pip install torch torchvision\n",
-    "import sys\n",
-    "import torch\n",
-    "if torch.__version__=='1.6.0+cu101' and sys.platform.startswith('linux'):\n",
-    "    !pip install pytorch3d\n",
-    "else:\n",
-    "    !pip install 'git+https://github.com/facebookresearch/pytorch3d.git@stable'\n",
-    "    \n",
     "# we also install chumpy as it is needed to load the SMPL model pickle file\n",
     "!pip install chumpy"
    ]