Revert "Don't validate fact check email contents"

This reverts commit 3e41497aa6dcaeea38c24ac53d6242a0e2846f99.

Conflicts:

	app/models/workflow.rb

We no longer validate all text fields as safe Govspeak, so a cause of many false positives in processing fact check responses is removed. It is conceivable that we will get false positives when we validate the emails as Safe HTML.

When this is released, we should upgrade publisher and remove a matching hack from Publisher:
https://github.com/alphagov/publisher/blob/master/app/models/enhancements/user.rb#L13