Installing Previous mynewt Fails for version 1.6 Onwards

[t3zeng]

Installation for mynewt 1.6 onwards no longer points to the correct binary release directory thanks to the name change first introduced with this commit:
JuulLabs-OSS/binary-releases@9180194

Appending @ to version the brew installation of mynewt will now throw an error like so:

Error: Failed to download resource "[email protected]"
Download failed: https://github.com/JuulLabs-OSS/binary-releases/raw/master/mynewt-newt-tools_1.8.0/mynewt-newt%401.8-1.8.0.big_sur.bottle.tar.gz

The script is attempting to download the bottle with @version_num in its name and failing