Comments: Allow `wp_update_comment()` to return `WP_Error()`.

The `wp_update_comment_data` filter introduced in 4.7 allows comment data to be filtered before it is updated in the database.

The patch aims to handle `WP_Error` as the filter above return value in a similar manner as is done for `wp_new_comment()`.


Fixes #39732.

Props: enricosorcinelli, swissspidy, gkloveweb, jnylen0, jbpaul17, afercia, SergeyBiryukov, audrasjb, imath, davidbaumwald.

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