Revert "Add tests using diff-pdf" and related commits

This reverts commit 6e9b6b2e5a86dee6a156a2772aea5f73b8dbbf68.
This reverts commit 6528b0b2d76ffbc586da44be47af1eb28ef17a4c.
This reverts commit f9ea182d24e146edca99c5c72d7503bc811d9a42.