Make final branch the default

Currently the master branch is the default, so when folks search for this repo, they don't see any KMM code. Of course the README explains to look in the final branch, but if you make this branch the default, your sample will be more accessible.

Review the repository's current master and final branches, along with the README's guidance about the final branch. Update the repository default-branch setting so final is selected, then verify that visitors see the KMM code when opening the repository.

Written by the indexing model from the issue text.