Privacy: Simplify the logic for updating the meta values for personal data...

Privacy: Simplify the logic for updating the meta values for personal data export requests from absolute to relative paths.

Follow-up to [48127].

See #44038.
Built from https://develop.svn.wordpress.org/trunk@48330


git-svn-id: https://core.svn.wordpress.org/trunk@48099 1a063a9b-81f0-0310-95a4-ce76da25c4cd