Remove 'underscores' scss files as a dependency

[bacoords]

It's time to reevaluate whether we need the the /src/sass/underscores/ dependency at all. It doesn't exist in the parent theme and much of the code is duplicated in the _understrap.scss file anyway.

I suggest we delete the directory and remove @import "assets/underscores"; from /src/sass/child-theme.scss.

[0dp]

I raised this assumption long time ago. It's time imo to move away from the 'based on underscores'

Also the only dependency we are using from the npm package is the skip link i think

[bacoords]

I assume we'll always keep 'based on underscores' for SEO, visibility, legacy reasons. Plus it's in the name Understrap (not that a new name would be the worst thing), but since we don't even pull these SCSS files in the parent theme, I see no reason to keep them here.

[kirannasim]

just removed underscores SCSS files

https://github.com/understrap/understrap-child/pull/343