Rename "SDK" -> "Developer Tools" in documentations (OSS files) (#5238)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/5238

Part of the bigger "sdk" rename to "devtools" task, context in [post](https://fb.workplace.com/groups/222849770514616/permalink/467450562721201/). This diff replaces "SDK" with "Developer Tools" in the documentations.

Reviewed By: dbort

Differential Revision: D62462792

fbshipit-source-id: 18a46779a9e6d7fb782f563fe73f7c612afc4838