Referencing nonexistent "sam-dev-python" git tag for the TinyMPC repository

[xavier-guardian]

The top level CMakeLists.txt references a nonexistent tag for the TinyMPC Repo. This prevents installing with pip.

FetchContent_Declare(
  tinympc
  GIT_REPOSITORY https://github.com/TinyMPC/TinyMPC.git
  GIT_TAG sam-dev-python
)

[sschoedel]

Changed to point to a valid commit instead. Thank you!