Changeset 51455 for trunk

Bundled Themes: Bump bundled theme versions for WordPress 5.8.

This bumps the version for all bundle themes in preparation for release with WordPress 5.8. The new versions are as follows:

• Twenty Twenty-One: 1.4
• Twenty Twenty: 1.8
• Twenty Nineteen: 2.1
• Twenty Seventeen: 2.8
• Twenty Sixteen: 2.5
• Twenty Fifteen: 3.0
• Twenty Fourteen: 3.2
• Twenty Thirteen: 3.4
• Twenty Twelve: 3.4
• Twenty Eleven: 3.8
• Twenty Ten: 3.4

Props mukesh27, kapilpaul.
Fixes #53277.