Build/Test Tools: Stop generating unminified `.min` file.

The generated `wp-includes/assets/script-loader-packages.min.php` and `wp-includes/assets/script-modules-packages.min.php` files are not actually minified. Additionally, the only purpose they serve is to pass a different script handle to the script loader (`.min.js` vs. `.js`).

This eliminates the need for those files entirely since the difference in file size is negligible, and a human-readable version is more useful.

Props peterwilsoncc, desrosj.
Fixes #64909.

git-svn-id: https://develop.svn.wordpress.org/trunk@62072 602fd350-edb4-49c9-b593-d223f7449a82