add missing colab-install cell in example notebook (#1353)

Author: slayoo

examples/PySDM_examples/Rozanski_and_Sonntag_1982/figs_4_5_6.ipynb

@@ -28,6 +28,19 @@
     "- smoke tests"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import sys\n",
+    "if 'google.colab' in sys.modules:\n",
+    "    !pip --quiet install open-atmos-jupyter-utils\n",
+    "    from open_atmos_jupyter_utils import pip_install_on_colab\n",
+    "    pip_install_on_colab('PySDM-examples')"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 1,