Fixed broken link JSDoc's plugins directory

[removed-usr]

Fixed broken link with old route to plugins

Old broken link is not found

The plugin folder was moved, I found its new localization and by comparing a stale branch we can assure, that they indeed contain the same files

Stale backup https://github.com/jsdoc/jsdoc/tree/next/plugins

Old broken link https://github.com/jsdoc3/jsdoc/tree/master/plugins

Current https://github.com/jsdoc/jsdoc/tree/main/packages/jsdoc/plugins

The directories were changed in this jsdoc/jsdoc@b970691