Administration: Remove invalid attribute maxlength on number input.

Remove the `maxlength` attribute on screen options number of items per page input. Previously kept due to input inconsistencies in IE 11 and Edge, this invalid usage is no longer needed. IE 11 is no longer supported, and Edge now behaves according to specifications.

Props Arena94, afercia, joedolson.
Fixes #40610.

git-svn-id: https://develop.svn.wordpress.org/trunk@57272 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-admin/includes/class-wp-screen.php

@@ -1279,7 +1279,7 @@ public function render_per_page_options() {
 			<?php if ( $per_page_label ) : ?>
 				<label for="<?php echo esc_attr( $option ); ?>"><?php echo $per_page_label; ?></label>
 				<input type="number" step="1" min="1" max="999" class="screen-per-page" name="wp_screen_options[value]"
-					id="<?php echo esc_attr( $option ); ?>" maxlength="3"
+					id="<?php echo esc_attr( $option ); ?>"
 					value="<?php echo esc_attr( $per_page ); ?>" />
 			<?php endif; ?>
 				<input type="hidden" name="wp_screen_options[option]" value="<?php echo esc_attr( $option ); ?>" />