Revert "Fix #17870: XSS in adm_config_report.php"

This reverts commit b509ab3.

The wrong string API call was used, it should have been
string_attribute() and not string_display_line(). Thanks to
Paul Richards for pointing this out.

adm_config_report.php

@@ -486,7 +486,7 @@ function print_option_list_from_array( array $p_array, $p_filter_value ) {
 				<label for="config-option"><span><?php echo lang_get( 'configuration_option' ) ?></span></label>
 				<span class="input">
 					<input type="text" name="config_option"
-						value="<?php echo string_display_line( $t_edit_option ); ?>"
+						value="<?php echo $t_edit_option; ?>"
 						size="64" maxlength="64" />
 				</span>
 				<span class="label-style"></span>