I18N: Mark screen reader strings as such with translator comments.

This aims to provide better context for translators and make it easier to determine that some strings contain hidden accessibility text and are not displayed in the UI.

Props kebbet, mercime, pavelevap, ocean90, swissspidy, Chouby, jipmoors, afercia, desrosj, costdev, audrasjb, SergeyBiryukov.
Fixes #29748.
Built from https://develop.svn.wordpress.org/trunk@55276


git-svn-id: http://core.svn.wordpress.org/trunk@54809 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update.php

@@ -924,7 +924,12 @@ function wp_print_admin_notice_templates() {
 							printf( __( '%s updates failed.' ), '{{ data.errors }}' );
 							?>
 						<# } #>
-						<span class="screen-reader-text"><?php _e( 'Show more details' ); ?></span>
+						<span class="screen-reader-text">
+							<?php
+							/* translators: Hidden accessibility text. */
+							_e( 'Show more details' );
+							?>
+						</span>
 						<span class="toggle-indicator" aria-hidden="true"></span>
 					</button>
 				<# } #>