remove check by incorrect regex

Author: miya0001

features/db-search.feature

@@ -702,6 +702,10 @@ Feature: Search through the database
     Then STDOUT should be empty
 
     When I try `wp db search 'unfindable' --regex --regex-flags='abcd'`
+    Then STDERR should be:
+      """
+      Error: The regex '/unfindable/abcd' fails.
+      """
     Then the return code should be 1
 
     When I run `wp db search '[0-9é]+?https:' --regex --regex-flags=u --before_context=0 --after_context=0`

src/DB_Command.php

@@ -820,10 +820,6 @@ public function search( $args, $assoc_args ) {
 
 		if ( ( $regex = \WP_CLI\Utils\get_flag_value( $assoc_args, 'regex', false ) ) ) {
 			$regex_flags = \WP_CLI\Utils\get_flag_value( $assoc_args, 'regex-flags', false );
-			// http://php.net/manual/en/reference.pcre.pattern.modifiers.php
-			if ( $regex_flags && ! preg_match( '/^(?!.*(.).*\1)[imsxeADSUXJu]+$/', $regex_flags ) ) {
-				WP_CLI::error( "Incorrect PCRE modifiers." );
-			}
 			$regex_delimiter = \WP_CLI\Utils\get_flag_value( $assoc_args, 'regex-delimiter', '/' );
 			if ( '' === $regex_delimiter ) {
 				$regex_delimiter = '/';