Fix headings for 08_semantic_router.ipynb

Author: paololazzari

docs/user_guide/08_semantic_router.ipynb

@@ -515,7 +515,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Add route references"
+    "## Add route references"
    ]
   },
   {
@@ -550,7 +550,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Get route references"
+    "## Get route references"
    ]
   },
   {
@@ -623,7 +623,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Delete route references"
+    "## Delete route references"
    ]
   },
   {