[Doc] Convert docs to use colon fences (#12471)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/source/generate_examples.py

@@ -57,9 +57,9 @@ class Index:
 
     def generate(self) -> str:
         content = f"# {self.title}\n\n{self.description}\n\n"
-        content += "```{toctree}\n"
+        content += ":::{toctree}\n"
         content += f":caption: {self.caption}\n:maxdepth: {self.maxdepth}\n"
-        content += "\n".join(self.documents) + "\n```\n"
+        content += "\n".join(self.documents) + "\n:::\n"
         return content