Disable caching for sprockets for now

What does this MR do?

Apparently our sprocket caching is not able to pick up changes in imported scss. e.g. application.scss imports a bunch of other files, but that is not visible to sprockets, so it doesn't invalidate the cache if one of those imported files is changed.

What are the relevant issue numbers?

See https://gitlab.com/gitlab-org/gitlab-ce/issues/57431

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer