Revert "Merge branch 'remove-deprecated'"

This reverts commit 38321b114e87a2fc8560f7651890aa1b7c2c2362, reversing
changes made to 048d6c0aefec9f233a77e9160f426cf2fed1b7f6.

arel 5.0.0 was already released and it will be safer to not remove
deprecated code in a stable release. master branch already contains
these removals so we can do a major release including they.