Update patch version for 3.15

Author: josh-wong

docusaurus.config.js

@@ -78,7 +78,7 @@ const config = {
                 label: '3.15',
                 path: 'latest', // When a new version is released and this is no longer the current version, change this to the version number and then delete this comment.
                 banner: 'none',
-                className: '3.15.3',
+                className: '3.15.4',
               },
               "3.14": { // When a new version is released and this is no longer the current version, change this to the version number and then delete this comment.
                 label: '3.14',