Revert "Merge pull request #10337 from eimermusic/fix_template_digestor_lookup"

This reverts commit b4239622afc4f3f73808fd0c97512f3a534e07dd, reversing
changes made to f99ce3c188f5dde57e2ff63e6a22363c62f0a4cd.

Reason: This broke the build
https://travis-ci.org/rails/rails/jobs/6629894
fixes warning in the AR test suite
ActiveRecord -> Active Record