Upgrade/Install: Return a more appropriate HTTP response status code (`409 Conflict`) if the `wp-config.php` file already exists.

Props linyows, ocean90.
Fixes #42466.
Built from https://develop.svn.wordpress.org/trunk@47478


git-svn-id: http://core.svn.wordpress.org/trunk@47267 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/setup-config.php

@@ -63,7 +63,8 @@ if ( file_exists( ABSPATH . 'wp-config.php' ) ) {
 			__( 'The file %1$s already exists. If you need to reset any of the configuration items in this file, please delete it first. You may try <a href="%2$s">installing now</a>.' ),
 			'<code>wp-config.php</code>',
 			'install.php'
-		) . '</p>'
+		) . '</p>',
+		409
 	);
 }
 
@@ -75,7 +76,8 @@ if ( @file_exists( ABSPATH . '../wp-config.php' ) && ! @file_exists( ABSPATH . '
 			__( 'The file %1$s already exists one level above your WordPress installation. If you need to reset any of the configuration items in this file, please delete it first. You may try <a href="%2$s">installing now</a>.' ),
 			'<code>wp-config.php</code>',
 			'install.php'
-		) . '</p>'
+		) . '</p>',
+		409
 	);
 }
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47476';
+$wp_version = '5.5-alpha-47478';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.