Minor changes to ROS 2 project configuration manual.

Change summary

Adjusted version of O3DE in ROS 2 project setup, removed USE_PHYSX5 macro from default snippet.

[x] Descriptive active voice - Do descriptive sentences have a clear subject and action verb?
[x] Answer the question at hand - Does the documentation answer a what, why, how, or where type of question?
[x] Consistency - Does the content consistently follow the Style Guide?
[x] Help the user - Does the documentation show the user something meaningful?