Emojis not standard across supported book formats

[pb-amy]

Prerequisites

• [x] Can you reproduce the behavior you wish to address with all plugins except Pressbooks deactivated?
• [x] Are you running the latest version of Pressbooks, the latest version of McLuhan, and the latest version of WordPress?
• [x] Are you experiencing the issue while using this book theme?
• [x] Did you perform a cursory search to see if your bug or enhancement is already listed?

Description

• the text ":)" shows up as it should on eub but not on pdf
• Issue is reproducible upon export and import
• When user initially sent in the bug, it was working on epub but not on pdf. The user has since made modifications to it which has made it not visible on both epub and pdf.
• Issue across multiple themes, does not seem to be affected by theme options (global or pdf options) -> defaulting the options do not change anything
• CSS also not an issue
• defaulting plugins does not fix the issue
• went into settings>export and chose email validation logs to be emailed but nothing shows up in email (either wordpress doesn't see it as an error or the email function is broken)
• plugin

visual editor:

epub:

pdf:

Steps to Reproduce

1. Go here and export PDF and epub versions. Notice that it does not print ":)"

Expected behavior:

Actual behavior:

System Information