Bump vendor/github.com/rails/sprockets from 2fe13f2 to 4dff018

Bumps [vendor/github.com/rails/sprockets](https://github.com/rails/sprockets) from `2fe13f2` to `4dff018`.
- [Release notes](https://github.com/rails/sprockets/releases)
- [Commits](rails/sprockets@2fe13f2...4dff018)

---
updated-dependencies:
- dependency-name: vendor/github.com/rails/sprockets
  dependency-version: 4dff018b9271c37b09889e829f8926d1c5379731
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]