Log Message:
misc/ruby-sprockets: update to 4.0.2

Update ruby-sprockets to 4.0.2.

## 4.0.2

- Fix `etag` and digest path compilation that were generating string with \ 
invalid digest since 4.0.1.

## 4.0.1

- Fix for Ruby 2.7 keyword arguments warning in `base.rb`. \ 
[#660](https://github.com/rails/sprockets/pull/660)
- Fix for when `x_sprockets_linecount` is missing from a source map.
- Fix subresource integrity to match the digest of the asset.