[rush] update `rush-pnpm update` to update the pnpm-config.json catalog data

The native `pnpm update` updates any catalogs defined in the `pnpm-workspaces.yaml` file with whatever changes it would have otherwise made to the package.json files. 

With `catalogs` now living in pnpm-config.json for Rush monorepos, it'd be nice to have the `rush-pnpm update` behaviour update that location instead.   

Currently, when you run the command, it passes but nothing is updated. 