Set launch file migration guide ToC depth to 2 to ease navigation (#5919)

Signed-off-by: Christophe Bedard <[email protected]>
(cherry picked from commit dd8e89f)

Author: christophebedard

source/How-To-Guides/Migrating-from-ROS1/Migrating-Launch-Files.rst

@@ -10,7 +10,7 @@ Migrating Launch Files
 ======================
 
 .. contents:: Table of Contents
-   :depth: 1
+   :depth: 2
    :local:
 
 While launch files in ROS 1 are always specified using `XML <https://wiki.ros.org/roslaunch/XML>`__ files, ROS 2 supports both XML and YAML files.