Update dowhy_lalonde_example.ipynb

Added numbering to each of the sections to match the "1. Load the data"

Signed-off-by: Emre Kıcıman <emrek@microsoft.com>

docs/source/example_notebooks/dowhy_lalonde_example.ipynb

@@ -69,7 +69,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Run DoWhy analysis: model, identify, estimate"
+    "## 2. Run DoWhy analysis: model, identify, estimate"
    ]
   },
   {
@@ -101,7 +101,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Interpret the estimate\n",
+    "## 3. Interpret the estimate\n",
     "The plot below shows how the distribution of a confounder, \"married\" changes from the original data to the weighted data. In both datasets, we compare the distribution of \"married\" across treated and untreated units."
    ]
   },
@@ -119,7 +119,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Sanity check: compare to manual IPW estimate"
+    "## 4. Sanity check: compare to manual IPW estimate"
    ]
   },
   {