Accessibility: Comments: Replace @ with at in the displayed date format.

The `@` symbol makes sense in the context of email addresses, but does not have a universal meaning in the context of dates.

Props birgire, afercia, audrasjb, SergeyBiryukov.
Fixes #47893.

git-svn-id: https://develop.svn.wordpress.org/trunk@46084 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/comment.php

@@ -209,6 +209,7 @@ switch ( $action ) {
 			__( '%1$s at %2$s' ),
 			/* translators: Comment date format. See https://secure.php.net/date */
 			get_comment_date( __( 'Y/m/d' ), $comment ),
+			/* translators: Comment time format. See https://secure.php.net/date */
 			get_comment_date( __( 'g:i a' ), $comment )
 		);
 		if ( 'approved' === wp_get_comment_status( $comment ) && ! empty( $comment->comment_post_ID ) ) {