Fix: biographical info not erased during personal data erasure (#64282)

[iflair]

Trac ticket: https://core.trac.wordpress.org/ticket/64282

Summary

This patch ensures the biographical information (user meta 'description') is removed
as part of the personal data erasure process.

What I changed

1. Added a personal data eraser function wp_user_personal_data_eraser() in wp-includes/user.php
   that deletes description user meta during erasure.
2. Registered the eraser via the wp_privacy_personal_data_erasers filter (wp-includes/default-filters.php).

Testing

• Applied the patch and verified description meta is removed when erasing personal data.
• (If you ran tests locally, list them here.)

Notes

• Original Trac diff: 64282.diff
• Author: @iFlairWebTechnologies

Please let me know if you'd like me to split the changes, add unit tests, or adjust any naming.

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[github-actions]

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[mindctrl]

6.7.0 wouldn't be accurate here, but we can't say for sure if it would be 7.0 or some other version. Typically in this case, the recommended tag is something like this (which gets changed when committed to whichever version is being targeted):

I'd update all the other @since tags in this PR to match.

Suggested change

	* @since 6.7.0
	* @since n.e.x.t