Describe the bug

The rainbow emoticon causes the text that follows in the title to become strong, and the tag is showing up in notices when publishing posts.

To Reproduce

Steps to reproduce the behavior:

1. New post.
2. Type "🌈Testing!🌈".
3. Publish the post.

Notice that the title shown in the notice is: "🌈Testing!🌈"

Expected behavior

The publication notice shown should show the title as it was written.

Screenshots

Gutenberg	Aztec

Smartphone (please complete the following information):

• Device: iPhone 11 Pro Max Simulator
• OS: iOS 13.3
• Version NA

Additional context

This issue was first reported by @catehstn