[wmcb] Update submodule

Updates the windows-machine-config-bootstrapper submodule
to commit `0cfab036cefbe4d658b160d9ae80289ce1e1249f`.

Commands run:
```
cd windows-machine-config-bootstrapper
git fetch && git checkout 0cfab036cefbe4d658b160d9ae80289ce1e1249f
cd ..
```