Bump default theme versions for WordPress 7.2

[mukesh27]

Bundled themes will need a version bump for the 7.2 release.

Previously:

• #65322 - 7.1
• #64817 - 7.0
• #64069 - 6.9
• #63681 - 6.8.2
• #62990 - 6.8
• #62034 - 6.7
• #60701 - 6.6
• #59816 - 6.5
• #58832 - 6.4
• #57857 - 6.3
• #57689 - 6.2
• #56450 - 6.1
• #55754 - 6.0
• #54783 - 5.9
• #53277 - 5.8
• #52704 - 5.7
• #51919 - 5.6
• #50889 - 5.5
• #49743 - 5.4

This bumps the version for the upcoming release WordPress 7.2. Twenty Ten: 4.8.
Twenty Eleven: 5.3.
Twenty Twelve: 5.0.
Twenty Thirteen: 4.8.
Twenty Fourteen: 4.7.
Twenty Fifteen: 4.4.
Twenty Sixteen: 4.0.
Twenty Seventeen: 4.3.
Twenty Nineteen: 3.5.
Twenty Twenty: 3.3.
Twenty Twenty-One: 3.0.
Twenty Twenty-Two: 2.3.
Twenty Twenty-Three: 1.8.
Twenty Twenty-Four: 1.7.
Twenty Twenty-Five: 1.6.

Trac ticket: https://core.trac.wordpress.org/ticket/65875

## Use of AI Tools
AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Applying the version, date, and changelog updates across the theme files, and checking header consistency. All changes were reviewed and validated by me.