Fix grammatical error in class-wp-ability.php

[hbhalodia]

## Issue

While reviewing the codebase for the Abilities API, I used Copilot to check for grammatical issues across the files. During this review, I noticed a minor grammatical error that is easy to miss when scanning multiple files at once.

• In the file class-wp-ability.php, there is a grammatical mistake on the following line: ​https://github.com/WordPress/wordpress-develop/blob/2d8f37d2a8ba53f2fa286dbf0e6b6399cf3c0784/src/wp-includes/abilities-api/class-wp-ability.php#L196

• Current text: caught and converted to a WP_Error when by WP_Abilities_Registry::register().

• Proposed correction: caught and converted to a WP_Error by WP_Abilities_Registry::register().

• The word “when” is redundant and should be removed to correct the sentence.

Trac ticket: https://core.trac.wordpress.org/ticket/64503

[westonruter]

In 61483:

Docs: Fix grammatical error in docs for WP_Ability::prepare_properties().

Follow-up to [61032].

Props hbhalodia.
See #64098.
Fixes #64503.