Use python 3.7 on Google Colab

Author: seisman

python-demo.ipynb

@@ -52,11 +52,11 @@
     "!bash ./Miniconda3-latest-Linux-x86_64.sh -bfp /usr/local\n",
     "!conda update conda -y -q\n",
     "!conda config --prepend channels conda-forge\n",
-    "!conda install -q -y --prefix /usr/local python=3.9 pygmt\n",
+    "!conda install -q -y --prefix /usr/local python=3.7 pygmt\n",
     "\n",
     "import sys\n",
     "import os\n",
-    "sys.path.append('/usr/local/lib/python3.9/site-packages')\n",
+    "sys.path.append('/usr/local/lib/python3.7/site-packages')\n",
     "os.environ[\"GMT_LIBRARY_PATH\"]=\"/usr/local/lib\""
    ]
   },