Revert "Merge pull request #3453 from dimagi/release-case-list-icons"

This reverts commit 20e4706eebc715f6aa1f1d0b9e481b62766668e9, reversing
changes made to 093e567a2497e9c5ad8c24babaf0076b029295cf.
release case list icons in feature preview
Merge branch 'master' into icons-feature-preview

Conflicts:
	corehq/feature_previews.py
Merge pull request #3462 from dimagi/icons-feature-preview

Icons feature preview