Mistaken instructions for manually installing the macOS binary.

https://github.com/exercism/interactive-cli-walkthrough/blob/53b89e180b72bd6e0df88769362104a08a40090c/contents/mac/create_bin_folder.tw2#L41 instructs the user to run
```bash
mv ~/Downloads/BINARY_NAME ~/bin
```
however, the binary is in the extracted directory ie. `~/Downloads/exercism*/BINARY_NAME`.

I would submit a PR for this but I'm not sure how to make it dependant on the architecture because the extracted folder name is different depending on which architecture the user is on.

Another option is to change the instruction to
```bash
mv ~/Downloads/exercism*/BINARY_NAME ~/bin
```
but may not be desired because they may have another folder in there.