fixed a couple of issues that made the notebook not work in colab (#1460)

* fixed a couple of issues that made the notebook not work in colab

i fixed a couple of issues that made the notebook not work in colab 
1. it downloaded incompatible versions of pytorch and cuda + the conda command doesnt do anything in colab since there is no conda in colab idk w y wanna do about that - The commit of 2 days ago only changes the conda command version and not the pip command which is used while isntaling mcvv
2. /demo.png doesnt exist in colab so i added a wget to download some cityscapes photo from the internet and run inference on that photo
3. i think it would be optimal to have 2 notebooks. 1 for running locally when cloning your git branch and one to run in google colab.

* Update demo/MMSegmentation_Tutorial.ipynb

* Update demo/MMSegmentation_Tutorial.ipynb

* Update demo/MMSegmentation_Tutorial.ipynb

* Update demo/MMSegmentation_Tutorial.ipynb

* Update demo/MMSegmentation_Tutorial.ipynb

Co-authored-by: Miao Zheng <76149310+MeowZheng@users.noreply.github.com>

demo/MMSegmentation_Tutorial.ipynb

@@ -69,7 +69,7 @@
     "# Install PyTorch\n",
     "!conda install pytorch=1.10.0 torchvision cudatoolkit=11.1 -c pytorch\n",
     "# Install MMCV\n",
-    "!pip install mmcv-full -f https://download.openmmlab.com/mmcv/dist/cu101/torch1.6/index.html"
+    "!pip install mmcv-full -f https://download.openmmlab.com/mmcv/dist/cu111/torch1.10/index.html"
    ]
   },
   {
@@ -156,8 +156,8 @@
    },
    "outputs": [],
    "source": [
-    "config_file = '../configs/pspnet/pspnet_r50-d8_512x1024_40k_cityscapes.py'\n",
-    "checkpoint_file = '../checkpoints/pspnet_r50-d8_512x1024_40k_cityscapes_20200605_003338-2966598c.pth'"
+    "config_file = 'configs/pspnet/pspnet_r50-d8_512x1024_40k_cityscapes.py'\n",
+    "checkpoint_file = 'checkpoints/pspnet_r50-d8_512x1024_40k_cityscapes_20200605_003338-2966598c.pth'"
    ]
   },
   {
@@ -185,7 +185,7 @@
    "outputs": [],
    "source": [
     "# test a single image\n",
-    "img = './demo.png'\n",
+    "img = 'demo/demo.png'\n",
     "result = inference_segmentor(model, img)"
    ]
   },